World Health Organisation Disability Assessment Schedule (WHODAS 2.0): development and validation of the Igbo version in patients with chronic low back pain

doi:10.21203/rs.3.rs-27535/v1

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Research article

World Health Organisation Disability Assessment Schedule (WHODAS 2.0): development and validation of the Igbo version in patients with chronic low back pain

https://doi.org/10.21203/rs.3.rs-27535/v1

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published 17 Nov, 2020

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Background

The leading cause of years lived with disability globally is low back pain (LBP). Chronic low back pain (CLBP) is responsible for the cost and disability associated with LBP, which is more devastating in low-income countries, particularly in rural Nigeria with one of the greatest global LBP burdens. No Igbo back pain specific measure captures remunerative/non-remunerative work outcomes. Disability measurement using these tools may not fully explain work-related disability and community participation, a limitation not evident in the World Health Organisation Disability Assessment Schedule (WHODAS 2.0). This study aimed to cross-culturally adapt the WHODAS 2.0 and validate it in rural and urban Nigerian populations with CLBP.

Methods

Translation, cultural adaptation, test–retest reliability and cross-sectional validity testing. WHODAS 2.0 was translated forwards and backwards by clinical/non-clinical translators. Translations were evaluated by expert review committee. The questionnaire was pre-tested among twelve rural Nigerian dwellers having CLBP. Cronbach’s alpha evaluating internal consistency; intraclass correlation coefficient and Bland–Altman plots investigating test–retest reliability; and minimal detectable change were examined in a convenient sample of 50 CLBP victims in rural and urban Nigeria. Spearman’s correlation analyses with the back-performance scale, Igbo Roland Morris Disability Questionnaire and eleven-point box scale; and exploratory factor analysis in a random sample of 200 adults with CLBP in rural Nigeria determined construct validity. Ceiling and floor effects were investigated in all participants.

Results

Translation was straight forward. Patient instructions were translated. ‘Waist pain/lower back pain’ was added to ‘illness(es)’ to make the measure relevant for this study whilst allowing for future studies of other conditions. The Igbo phrase for ‘family and friends’ was used to better represent ‘people close to you’ in item D4.3. The Igbo-WHODAS had good internal consistency (α = 0.75–0.97); intra class correlation coefficients (ICC = 0.81–0.93); standard error of measurements (5.05–11.10) and minimal detectable change (13.99–30.77). Igbo-WHODAS correlated moderately with performance-based disability, self-reported back pain-specific disability and pain intensity, with a seven-factor structure and no floor and ceiling effects.

Conclusions

Igbo-WHODAS can be used clinically or for research as it is a psychometrically sound measure of self-reported disability.

Orthopedics

Disability

Cross-cultural

Psychometric

Igbo World Health Organisation Disability Assessment Schedule

Africa

Nigeria

Rural

Low back pain

Disability is an encompassing label for impairments, activity limitations and participation restrictions, which result from the interaction between a health condition, and contextual (environmental and personal) factors [1]. Disability is a multidimensional concept including body function (physiological and psychological) and structure (anatomy); activities and participation; and environmental factors [1]. According to the World Health Survey, the global adult (≥ 18 years) prevalence of disability is 15.6%; ranging from 11.8% in higher income countries to 18.0% in lower income countries most of which are African countries [2]. Among people aged ≥ 60 years, disability prevalence is much higher, ranging from 43.4% in lower income countries to 29.5% in higher income countries. These prevalence rates are likely grossly underestimated in Africa where only a few people who have severe disability are reported [2].

The leading cause of years lived with disability globally is low back pain (LBP) according to global burden of disease studies [3, 4]. LBP is predominantly regarded as a chronic condition because one year after its first onset nearly 80% of patients still have pain [5]. Most of the cost and disability associated with LBP is due to chronic low back pain (CLBP) [6]. These consequences can be more overwhelming in low income countries, particularly in rural Africa with high levels of poverty and poor health services. Nigeria has one of the greatest burdens of LBP globally. The prevalence rate of LBP ranging between 72–85% in rural Nigeria [7], is much higher than the 39% in urban Nigeria [8]; and 14–51% in other African countries [9]. Furthermore, the point prevalence rate of 33–40% in Nigeria is greater than the 10–33% in high income countries including the UK, Canada and Belgium [10].

Measures for LBP disability are mostly self-reported due to their low cost and ease of administration including reduced patient burden and non-invasiveness. Moreover, assessment of disability through self-report may be comparable to objective disability measurements [11] and is sometimes more reliable than objective assessments since disability constructs such as participation restriction, may be more directly measured subjectively through self-reports. In contrast, performance-based disability measures may be impairment focused overlooking other important dimensions of disability such as activity limitations and participation [12]. This is limiting as people with impairment may not experience disability, or do so at varying levels depending on personal, physical and social barriers/facilitators in different contexts.

There are several back pain specific self-report measures, the most commonly used being the Roland-Morris Disability Questionnaire and the Oswestry Low Back Pain Disability Questionnaire. However, none of these measures cover remunerative or non-remunerative work outcomes, which are often regarded as an aspect of participation [13, 14]. This implies that disability measurement using these tools may not fully explain work-related disability, community participation, and other domains of participation which are likely to be context specific. This limitation is not evident in the World Health Organisation Disability Assessment Schedule (WHODAS 2.0), an international classification of functioning, disability and health (ICF) based generic disability measure. The measure has distinct activity and participation domains, that include work-related disability and community participation [15]. Therefore, the WHODAS 2.0 might be one of the best measures for assessing LBP disability – being the most supportive of the biopsychosocial disability model.

However, the original WHODAS 2.0 is in English [15], making it difficult to use in clinical and epidemiological studies for low literate non-English speaking people in rural and urban Nigeria. Therefore, this study aims to translate, culturally adapt and investigate the validity and reliability of the Igbo version of the WHODAS 2.0 in rural and urban populations in Nigeria.

Ethical concerns

King’s College London (Ref: BDM/13/14–99) and University of Nigeria Teaching Hospital (Ref: UNTH/CSA/329/Vol.5) gave ethical approvals. The World Health Organisation gave permission to adapt the measure.

Study designs

Cross-cultural adaptation, test-retest measurements and cross-sectional study of psychometric properties.

Outcome measurement tools

World Health Organisation Disability Assessment Schedule (WHODAS 2.0)

The WHODAS 2.0 is a comprehensive measure that assesses disability within the ICF biopsychosocial model emphasizing the six domains of cognition, mobility, self-care, getting along with people, life activities and participation – including work-related disability [15]. The measure has good face and content validity, construct validity, internal consistency, test-retest reliability and responsiveness. The Cronbach’s alpha ranges between 0.94 and 0.98; test-retest reliability ranges between 0.93 and 0.98; and sensitivity to change ranges between 0.46 and 1.38 [15]. The 36-item interviewer-administered version, with simple and complex scoring methods was used due to its relevance in populations with low literacy. Simple scoring involves assigning values “none” =1, “mild” =2 “moderate” =3, “severe” =4 and “extreme” =5, which are simply added up without weighting of individual items. However, this method may not be comparable across populations and conditions. Therefore, the complex scoring method was used in this paper. Complex scoring is an “item-response-theory” (IRT) based scoring that takes into consideration multiple levels of difficulty for each item. It involves summing recoded item scores in each domain, summing all six domain scores, and converting the summary score into a metric ranging from 0 (no disability) to 100 (full disability) [15].

Igbo Roland Morris Disability Questionnaire (Igbo-RMDQ)

RMDQ is a valid and reliable measure of self-reported LBP disability; and recommended as a core outcome measure for LBP clinical trials [12]. It is easy to administer, understood effortlessly, and is the best disability measure for population-based or primary care-based studies. The Igbo-RMDQ, adapted from the original RMDQ, is a twenty-four item back specific self-report disability measure with possible scores of 0 or 1 for each item. A score of 24 is the highest possible disability level and 0 is no disability. It has good face and content validity, construct validity, internal consistency, test-retest reliability and responsiveness [12]. It has a global Cronbach’s alpha score of 0.91; test-retest reliability of 0.84; and a 2-3-point change from baseline means clinical significance [12].

Back performance scale (BPS)

BPS is a back-specific performance-based measure of mobility-related limitation that is scored by external evaluator [16]. The instructions are simple and involves instructing participants to perform five physical performance tests (sock test, pick-up test, roll-up test, finger-tip-to-floor test and lift test) involving mobility of the trunk. Sock test involves simulating putting on a sock normally from sitting. Pick-up test involves picking up a piece of paper from the floor normally. For the roll-up test, participant rolls up slowly from supine lying to long sitting with both arms relaxed. Finger-tip-to-floor test involves standing on the floor with feet 10 centimetres apart. There is then forward bending with straight knees and attempts to touch the floor with the fingertips. The distance between the floor and the fingertips is then measured in centimetres. The lift test involves a participant repeating the lifting of a 5-kilogram box from the floor to a 76 cm table and back to the floor for one minute, and the number of lifts recorded. Each test has scores between 0 and 3 depending on the difficulty or ease with which they are performed. A total score of 15 indicates maximum disability with 0 meaning no disability [16]. The BPS has a good internal consistency of 0.73, moderate correlations with self-reported disability (r = 0.454) confirming construct validity, and a good test-retest reliability of 0.91 [16, 17].

Eleven-point box scale (BS-11)

As CLBP is painful and pain is a predictor of CLBP disability, pain intensity assessment was required. BS-11 is a single item eleven-point numeric scale of pain intensity [18]. It consists of eleven numbers (0 to 10) in boxes. Zero signifies ‘no pain’ and 10 is ‘pain as bad as you can imagine’ or ‘worst pain imaginable’. The measure is easily understood among low literate populations in Nigeria [19].

Cross-cultural adaptation process

Translation is the linguistic rephrasing of a questionnaire into a different language whereas cross-cultural adaptation involves translation and cultural adaptation to enable the content validity of the instrument to be at a similar conceptual level in the new (intended) context [12].

Participants

A clinical physiotherapists with 18 years of clinical experience practising in Nigeria, three non-clinical translators (Igbo linguistic expert, business woman who studied linguistics and microbiologist who left Nigeria at 7 years old and grew to adulthood as a native English speaker in England), an expert review committee (English health psychologist and English academic physiotherapist working in the United Kingdom; Igbo clinical psychologist and Igbo clinical physiotherapist working in Nigeria), and a convenience sample of 12 adults living with non-specific CLBP in rural Nigeria who had participated in a previous study [19] and gave informed consent, were involved in the cross-cultural adaptation process.

Procedure

The original WHODAS 2.0 was translated into Igbo and culturally adapted using internationally recognised evidence-based guidelines [20, 21].

First step – the WHODAS 2.0 was forward translated independently from English to Igbo by one bilingual clinical physiotherapist and one bilingual non-clinical professional translator (who is an Igbo linguistic expert) to obtain two Igbo versions: T1 and T2 respectively. The forward translators were both native Igbo speakers fluent in English. For the physiotherapist, items were explained to ensure an understanding of the construct being assessed by the questionnaire in order to provide psychometric equivalence with the original WHODAS 2.0. For the non-clinical translator, items were not defined to ensure that the language and expressions used in the translation reflected the lay language routinely employed by people in Igbo populations.

Second step – a discussion between the two forward translators, mediated by the bilingual (English and Igbo) lead author resulted in the synthesis of T1 and T2 to produce one Igbo version: T-12. The lead author compared the translations, noted and recorded all discrepancies.

Third step – the synthesized Igbo version (T-12) was back translated from Igbo to English by two back non-clinical translators blinded to the original WHODAS 2.0 to produce two back-translated English versions: BT1 and BT2. The back translators included the businesswoman who studied linguistics, and the microbiologist who grew up as a native English speaker in England. Back-translation provided the validation that the adapted WHODAS 2.0 was reproducing the meaning in the original WHODAS 2.0.

Fourth step – a pre-final Igbo version of the WHODAS 2.0 was produced following several meetings of the expert review committee during which all translated versions of the measure (T1, T2, T-12, BT1 and BT2) were discussed, mediated by the lead author. The committee achieved semantic equivalence by exploring Igbo and English words of the same object to determine if they meant exact things, if the same terms could have several meanings, and if linguistic difficulties were encountered during the translations. The committee accomplished experiential equivalence with the original measure by ascertaining that items were experienced in the same way in the Western and Igbo cultures. The committee established comparable conceptual meanings for the words in the instructions, items, and responses in Igbo and Western cultures [20]. The Igbo words used in the translations were simple enough to be understood by anyone regardless of literacy.

Fifth step – twelve people living with CLBP in a rural Nigerian community [19] pre-tested the pre-final Igbo-WHODAS 2.0. The think-aloud cognitive interviewing procedure was used. This involved participants reading out each item and loudly verbalising their thoughts as they attempted to answer it. Participants finally stated if they did not understand any item, what they understood by each question, and the perceived meaning of their selected response(s). All responses were recorded verbatim. This procedure helped to maintain equivalence between the two settings ensuring face and content validity of the Igbo WHODAS 2.0.

Psychometric testing process

Participants (sample size calculation for test-retest reliability)

A minimum sample size of 27 is required to detect an intra-class correlation coefficient of 0.9 and a maximum width of 0.23 for a 95% confidence interval. A study for examining test-retest reliability was conducted with a convenience sample of 50 adults with CLBP who had no underlying serious pathology, radiculopathy or spinal stenosis. The participants were aged between 18 and 69 years and were recruited from rural and urban communities in Enugu State, South-eastern Nigeria. Informed consent was duly obtained prior to participation in the study.

Participants (sample size calculation for construct validity)

A correlation coefficient of 0.2 at a level of 0.05 with a power of 80% would require a sample size of 194. In a dataset with several high factor loading scores (> 0.80), a sample size of 150 would be sufficient for exploratory factor analysis (EFA). A representative random sample of 200 adults with CLBP were recruited from rural communities in Enugu State as part of a larger population-based study and discussed in detail therein [22]. They were screened to rule out underlying serious pathology, radiculopathy or spinal stenosis. Informed consent was obtained prior to participation in the study.

Procedure for psychometric testing

A significant proportion of rural dwellers in Nigeria are not literate. Therefore, community health workers (CHWs), the front line of rural Nigerian primary health care, were recruited and trained for interviewer-administration of the questionnaires. The training was aimed at minimising common survey errors. A representative sample of the population obtained through multistage cluster sampling prevented coverage error. An adequate sample size and gender stratification prevented sampling error. The use of validated measures and training CHWs to avoid administering the measures in ways that could introduce prejudice to participants’ responses reduced measurement error. Non-response error was avoided by ensuring that no items or scales were unanswered and that all recruited participants were assessed.

Collection and fidelity of data

CHWs screened participants by asking simple questions to exclude back pain due to malignancy, spinal fracture, infection, inflammation or cauda equina syndrome. They were then asked to describe the location of their pain with a body chart to confirm that pain was in the lower back. The Igbo-WHODAS 2.0, Igbo-RMDQ and BS-11 were then interviewer-administered with Likert scales presented to participants as ‘flash cards’ as each item was read out. ‘Back pain’ was read out to participants in place of ‘illness’. The BPS, which measures performance-based disability was then administered objectively.

For test-retest reliability, measures were completed at baseline and repeated seven to ten days post-baseline, with the same CHW collecting data on the two occasions from the 50 participants.

To test validity, measures were completed at one time-point cross-sectionally among the 200 participants.

Fidelity checks were done to avoid systematic differences in data collection. The CHWs were given post-training examinations, and only those that passed them were involved in data collection. This facilitated adherence to data collection protocols. Additionally, each CHW was visited by the lead author during data collection without previous warning to assess their data collection and recording.

Data analyses

IBM Statistical Package for Social Sciences version 22 (SPSS, Chicago, IL) was utilised. Normality of data was assessed using visual (normal distribution curve and Q-Q plot), and statistical (Kolmogorov-Smirnov, Shapiro-Wilk’s test and Skewness/Kurtosis scores) methods.

Reliability

Reliability is the ability of an instrument to measure consistently. Test–retest reliability evaluated how consistently the adapted WHODAS 2.0 consistently measured disability over time using intra-class correlation coefficient (ICC). ICC was calculated using a two-way random effects model (measurement errors arising from either raters or subjects), using an absolute agreement definition between test-retest scores. 0.7, 0.8 and 0.9 signified good, very good and excellent ICCs [23]. Internal consistency (Cronbach’s alpha) depicts the extent to which all items in a test measure the same construct and was rated as weak (0–0.2), moderate (0.3 0.6) and strong (0.7–1.0) [24]. Bland-Altman plots, which accounted for the weakness of ICC that might indicate strong correlations between two measurements with minimal agreement, were employed to visually assess the agreement level between test-retest measurements by plotting mean scores against difference in total scores. Standard error of measurement (SEM) and minimal detectable change (MDC) were also used to investigate reliability. MDC is a statistical estimate of the smallest change detected by an instrument that corresponds to a noticeable change in ability which is not due to measurement error. MDC was calculated with the standard error of measurement (SEM), based on the distribution method, and the reliability of the measure which takes precision into account [25]. SEM was based on the standard deviation (SD) of the sample and the test-retest reliability (R) of the self-report measures, and was calculated with the equation [25]

SEM = SD √(1-R)

MDC was subsequently calculated with the equation [25]:

MDC = 1.96 * √2 * SEM

1.96: 95% confidence interval of no change;

√2: two assessments are involved in measuring change [25].

Validity

Construct validity assesses the extent to which a measure evaluates the construct it was intended to measure. The domain of construct validity assessed was convergent validity, which assesses whether two measures of the same/similar construct that are assumed to be theoretically related, are in fact related. This was investigated using Spearman’s correlation (non-parametric data) and was rated as weak (0-0.2), moderate (0.3–0.6), and strong (0.7-1.0). The WHODAS 2.0 assesses self-reported disability within the ICF multiple domains of cognition, mobility, self-care, getting along with people, life activities and participation – including work-related disability. Hence, Igbo-WHODAS 2.0 is expected to correlate at least moderately with the Igbo-RMDQ (measuring self-reported back pain-related disability), the BPS (objective measure of performance-based disability), and the Igbo-BS-11 (self-reported pain intensity measure and a predictor of self-reported disability [22, 26].

Exploratory factor analyses (EFA) was used to determine the number of factors influencing the Igbo-WHODAS (the items that go together – dimensionality). EFA was applied in line with the Kaiser Meyer Olkin (KMO) and the Bartlett’s test with eigenvalue for retention set at ⩾1.0 (Kaiser’s rule) [27]. Retained and excluded factors were also explored visually on a Scree plot. Promax (oblique) rotation, which assumes that factors can be related, was done, and factor loadings less than 0.3 were suppressed. Extraction was done using principal axis factoring. The number of factors and the fundamental relationships between the items were then compared with the factor structures of the original WHODAS 2.0 to augment any insight of possible differences in population characteristics.

Floor and ceiling effects

When a high proportion of participants score the highest or the lowest score, ceiling or floor effect respectively occurs, which implies that a measure is unable to discriminate between either extreme of the scale. A ceiling or floor effect was defined as 15% or more of the total sample of 250 participants scoring 0 or 100 on the Igbo-WHODAS 2.0 [28].

Cross-cultural adaptation participants

Table 1 highlights the socio-demographic characteristics of the participants that pre-tested the Igbo-WHODAS.

Table 1

Demographic characteristics of participants for cross-cultural adaptation
Demographic characteristics n = 12	Mean	Frequency	%
AGE	45 years
GENDER
Male		7	58.33
MARITAL STATUS
Married		11	91.67
Single		1	8.33
MAIN OCCUPATION
Non-manual workers		5	41.67
Manual workers		7	58.33
RELIGION
Protestant Pentecostal		10	83.33
Catholic		2	16.67
EDUCATIONAL LEVEL COMPLETED
Secondary		4	33.33
Primary		3	25.00
None		3	25.00
Tertiary		2	16.67
LITERACY
Illiterate		4	33.33
English		6	50.00
English and Igbo		2	16.67

Translation, pellucidity and cultural equivalence of Igbo-WHODAS

Translation was easy. The expert committee retained interviewer instructions in English as the interviewers are literate, and evidence from this population suggests that literate people found it easier to read English than Igbo [19]. Patient instructions were translated into Igbo. The committee added ‘waist pain/lower back pain’ to ‘illness(es)’ to make the measure back pain-specific for this study whilst allowing the measure to be used for other conditions in future studies. In item D1.3, translators wrote ‘understanding and finding out solutions’ as a translation of ‘analysing and finding solutions’. This was modified to the Igbo equivalent of ‘probing/exploring/researching’ and ‘find out/discover solutions’ by the expert review team to better reflect the original item as there is no Igbo word for ‘analyse’. The Igbo phrase for ‘people close to you’ also means ‘people near you’. The latter would not reflect the original item D4.3. Therefore, translators used the Igbo phrase for ‘family and friends’ to better represent ‘people close to you’. For item D6.1, forward translators translated ‘how you do things in your community’. Discrepancy was detected after back translation; hence the phrase was changed to ‘how you join in activities that are associated with your community’ by all translators to better reflect the original item. ‘…affected your heart or spirit’ was used in place of ‘emotionally affected’ in item D6.5 as there is no Igbo word for emotion; ‘deplete or affect’ was used in place of ‘drain’ in item D6.6; ‘to what extent’ rather than ‘how many’ was used to better reflect the original item in D6.1 through consensus of the translators and the review committee.

Psychometric properties of Igbo-WHODAS

Participants

Table 2 presents the socio-demographic characteristics of the test-retest reliability sample.

Table 3 presents the socio-demographic characteristics of the cross-sectional validity sample.

Table 2

Demographic characteristics of the test-retest reliability sample
Demographic characteristics n = 50	Mean (SD)	Frequency	%
AGE	45.2 years (11.55)
EDUCATION	13.3 years (7.14)
GENDER
Female		32	64.0
MARITAL STATUS
Married		37	74.0
Never married		8	16.0
Widowed		4	8.0
Separated		1	2.0
WORK STATUS
Paid work		25	50.0
Self-employed (own business or farming)		19	38.0
Keeping house/homemaker		2	4.0
Student		2	4.0
Non-paid work (volunteer or charity)		1	2.0
Unemployed (health reasons)		1	2.0
HABITATION
Rural		20	40.0
Urban		30	60.0

Table 3

Demographic characteristics of the cross-sectional validity sample
Demographic characteristics n = 200	Mean (SD)	Frequency	%
AGE	48.6 years (12.0)
EDUCATION	7.0 years (6.4)
GENDER
Female		112	56.0
MARITAL STATUS
Married		143	71.5
Widowed		31	15.5
Never married		22	11.0
Cohabiting		2	1.0
Separated		2	1.0
WORK STATUS
Self-employed (own business or farming)		125	62.5
Paid work		31	15.5
Non-paid work (volunteer or charity)		16	8.0
Keeping house/homemaker		13	6.5
Student		7	3.5
Unemployed (health reasons)		4	2.0
Unemployed (other reasons)		3	1.5
Retired		1	0.5

Findings from fidelity assessment

The CHWs strictly adhered to the interviewing styles recommended during the training by remaining neutral throughout the interviews. They did not react verbally or nonverbally to participants’ responses. They discouraged participants’ digression, distraction and inappropriate enquiries. They maintained the wording and sequence of questions in the measures and recorded data as appropriate. They provided only one answer to each item, written in the space provided for each item in each measure. Their assessment of performance-based disability was adequate, as they used tape measures adequately to assess 10 cm between the feet and measured the distance between the fingertips and the floor, for the finger-tip-to-floor test. The performance-based disability levels recorded by the first author and the CHWs were found to be similar for a random subsample of participants.

Reliability

Internal consistency was very good to excellent (α ≃ 0.8 to 0.9). Intraclass correlation coefficients were very good to excellent (ICC ≃ 0.8 to 0.9). Standard error of measurement and minimal detectable change were 5.05 and 13.99 for total scoring; 7.20 and 19.96 for cognition; 8.00 and 22.17 for mobility; 7.20 and 20.35 for self-care; 7.60 and 21.07 for getting along with people; 8.70 and 24.11 for life activities; 11.10 and 30.77 for participation. Acceptable agreements between test-retest values of the Igbo-WHODAS and its subscales were illustrated in Figs. 1 to 7 as mean differences were close to zero and most points were within the 95% limits of agreement of the mean differences (Table 4).

Table 4

Reliability of Igbo-WHODAS
Igbo-WHODAS total score Number of items: 36; Cronbach’s alpha global score: 0.97; ICC (95% CI): 0.93 (0.88, 0.96)
Cronbach’s alpha If Item Deleted
D1.1	D1.2	D1.3	D1.4	D1.5	D1.6	D2.1	D2.2
0.97	0.97	0.97	0.97	0.97	0.97	0.97	0.97
D2.3	D2.4	D2.5	D3.1	D3.2	D3.3	D3.4	D4.1
0.97	0.97	0.97	0.97	0.97	0.97	0.97	0.97
D4.2	D4.3	D4.4	D4.5	D5.1	D5.2	D5.3	D5.4
0.97	0.97	0.97	0.97	0.97	0.97	0.97	0.97
D5.5	D5.6	D5.7	D5.8	D6.1	D6.2	D6.3	D6.4
0.97	0.97	0.97	0.97	0.97	0.97	0.97	0.97
D6.5	D6.6	D6.7	D6.8
0.97	0.97	0.97	0.97
SEM: 5.05 MDC: 13.99
Igbo-WHODAS 2.0 (cognition) Number of items: 6; Cronbach’s alpha global score: 0.88; ICC (95% CI): 0.87 (0.77, 0.93)
Cronbach’s alpha If Item Deleted
D1.1	D1.2	D1.3	D1.4	D1.5	D1.6
0.85	0.87	0.86	0.87	0.86	0.88
SEM: 7.20 MDC: 19.96
Igbo-WHODAS 2.0 (mobility) Number of items: 5; Cronbach’s alpha global score: 0.91; ICC (95% CI): 0.90 (0.83, 0.94)
Cronbach’s alpha If Item Deleted
D2.1	D2.2	D2.3	D2.4	D2.5
0.89	0.88	0.90	0.89	0.88
SEM: 8.00 MDC: 22.17
Igbo-WHODAS 2.0 (self-care) Number of items: 4; Cronbach’s alpha global score: 0.75; ICC (95% CI): 0.82 (0.68, 0.90)
Cronbach’s alpha If Item Deleted
D3.1	D3.2	D3.3	D3.4
0.64	0.61	0.81	0.63
SEM: 7.20 MDC: 20.35
Igbo-WHODAS 2.0 (getting along with people) Number of items: 5; Cronbach’s alpha global score: 0.81; ICC (95% CI): 0.81 (0.66, 0.89)
Cronbach’s alpha If Item Deleted
D4.1	D4.2	D4.3	D4.4	D4.5
0.76	0.76	0.74	0.76	0.83
SEM: 7.20 MDC: 20.35
Igbo-WHODAS 2.0 (life activities) Number of items: 8; Cronbach’s alpha global score: 0.95; ICC (95% CI): 0.93 (0.87, 0.96)
Cronbach’s alpha If Item Deleted
D5.1	D5.2	D5.3	D5.4	D5.5	D5.6	D5.7	D5.8
0.94	0.94	0.94	0.94	0.94	0.94	0.94	0.94
SEM: 8.70 MDC: 24.11
Igbo-WHODAS 2.0 (participation) Number of items: 8; Cronbach’s alpha global score: 0.92; ICC (95% CI): 0.85 (0.73, 0.91)
Cronbach’s alpha If Item Deleted
D6.1	D6.2	D6.3	D6.4	D6.5	D6.6	D6.7	D6.8
0.90	0.91	0.92	0.91	0.91	0.91	0.91	0.90
SEM: 11.10 MDC: 30.77

Construct validity

Table 5 illustrates the total scoring of the Igbo-WHODAS and its subscales which correlated moderately (rs ≥ 0.3) with performance-based disability (BPS), self-reported disability (Igbo-RMDQ), and pain intensity (BS-11), except for the cognition and getting along subscales. There was a weak (rs = 0.19) but statistically significant correlation between the cognition subscale of the Igbo-WHODAS and performance-based disability. There was no correlation between the getting along subscale of the Igbo-WHODAS and performance-based disability.

A scree plot in Fig. 8 suggests a seven-factor structure of the Igbo-WHODAS, which is corroborated in Table 6. 62.79% of the items had factor loadings above 0.5 and 66.67% of the items loaded on their corresponding factor in the original measure. Factor 1 contains all the items of the original life (household and work/school) activities subscale in addition to two items of the original participation subscale – problem joining in community activities (D6.1), and problem doing things by oneself for relaxation/pleasure (D6.8); and one item of the original self-care subscale (staying by oneself for a few days).

Table 5

Spearman’s correlation between Igbo-WHODAS and self-reported back pain-specific disability, performance-based disability and self-reported pain intensity
	Igbo-RMDQ	BPS	BS-11
Igbo-WHODAS total	0.54**	0.34^**	0.56**
Igbo-WHODAS cognition	0.31**	0.19^**	0.44**
Igbo-WHODAS mobility	0.60**	0.35^**	0.50**
Igbo-WHODAS self-care	0.39**	0.28^**	0.25**
Igbo-WHODAS getting along	0.29**	0.09	0.31**
Igbo-WHODAS life activities	0.46**	0.33^**	0.54**
Igbo-WHODAS participation	0.50**	0.36^**	0.55**
**p < 0.01

Factor 2 contains all the items in the original getting along subscale in addition to one item of the original participation subscale D6.3 (living with dignity), and one item of the original cognition subscale D1.5 (understanding what people say).

Table 6

Exploratory factor analysis of the Igbo-WHODAS
n = 200	1	2	3	4	5	6	7
WHODAS D5.4	.904
WHODAS D5.1	.846
WHODAS D5.2	.799
WHODAS D5.8	.790
WHODAS D5.7	.730
WHODAS D5.3	.724
WHODAS D5.5	.720
WHODAS D5.6	.704
WHODAS D6.1	.503
WHODAS D3.4	.421
WHODAS D6.8	.305
WHODAS D4.4		.897
WHODAS D4.1		.812
WHODAS D4.3		.680
WHODAS D4.2		.549					.364
WHODAS D6.3		.503					.332
WHODAS D1.5		.484		.377
WHODAS D4.5		.413
WHODAS D2.4			.809
WHODAS D2.2			.720
WHODAS D2.5			.640
WHODAS D2.1			.624
WHODAS D2.3			.584
WHODAS D6.4			.546
WHODAS D6.5			.477
WHODAS D1.2				.759
WHODAS D1.1				.713
WHODAS D1.3				.680
WHODAS D1.4				.473
WHODAS D1.6		.411		.459
WHODAS D6.6					.912
WHODAS D6.7					.828
WHODAS D3.1			.310			.737
WHODAS D3.2						.689
WHODAS D3.3		.456				.480
WHODAS D6.2				.408			.421
KMO = 0.92 χ²= 4984.50***

Only factor loadings above 0.3 are shown; KMO = Kaiser-Meyer-Olkin measure of sampling adequacy; χ²= Bartlett’s test of sphericity tested with chi-square ***p < 0.001; Extraction Method: Principal Axis Factoring; Rotation Method: Promax with Kaiser Normalization; Rotation converged in 11 iterations.

Factor 3 matches the mobility subscale of the original measure, but with two additional items from the original participation subscale (time spent on back pain and emotional effects of back pain) loading on it. Factor 4 corresponds to the cognition subscale of the original measure except that one of the items in the original subscale (understanding what people say) loaded on the getting along factor. Factor 5 (participation subscale) had only two items, which were in the original subscale, loading on it (back pain drained financial resources and back pain caused family problems). It was the least precise subscale as items from the original participation subscale loaded on all factors except the self-care factor. Factor 6 matches the self-care subscale of the original measure except for one missing item (staying by yourself for a few days) that loaded on the life activities factor. Factor 7 had only one major item (barriers and hindrances in the world around one due to back pain) from the original participation subscale (Table 6).

Floor and ceiling effects

Eight (3.2%) participants scored 0 and no one (0%) scored 100 on the Igbo-WHODAS. 72 (28.8%) participants scored 0 on the cognition subscale, 27 (10.8%) scored 0 on the mobility subscale, 86 (34.4%) scored 0 on the self-care subscale, 62 (24.8%) scored 0 on the getting along subscale, 17 (6.8%) scored 0 on the life activities subscale, 21 (8.4%) scored 0 on the participation subscale; but no one (0%) scored 100 on any of the subscales. The Igbo-WHODAS 2.0 and its subscales did not have ceiling effect. However, floor effect was observed in cognition, self-care and getting along subscales.

The exact Igbo word equivalents for some English words were lacking during the translation of the WHODAS 2.0 which was resolved by using Igbo phrases that retained the conceptual meaning in the original items. This could be because Igbo language may be more adapted to colloquial speech than scientific writing [29]. Indeed, English is the official written language of instruction in Nigeria which may explain why literate Igbo Nigerians prefer to read/write English but speak Igbo informally. It was found that some Igbo words/phrases had multiple meanings depending on the context, which was resolved by using Igbo phrases with all possible meanings reflecting the original items.

The WHODAS 2.0 was straight forward to cross-culturally adapt, comprehend and was acceptable, as suggested by previous adaptations [30–32]. The cross-cultural adaptation confirmed its face and content validity. The lack of an Igbo word for ‘emotion’ in item D6.5 may reflect the unclear emotional concept in this culture where emotional distress is often expressed through somatisation [19, 33], which has been found in other non-western settings [34, 35]. ‘Affected your heart or spirit’ was therefore used to achieve conceptual equivalence.

Cronbach’s alpha of Igbo-WHODAS and its subscales ranging between 0.75–0.97 concurs with the original measure [15], and other adaptations [36–38]. However, the Cronbach’s alpha was slightly higher in the original measure possibly due to different population characteristics such as literacy.

Igbo-WHODAS and its subscales demonstrated reliability with ICCs that were very good to excellent (0.81–0.93). The good agreement shown in the Bland-Altman plots mirrors the original measure [15], and other adaptations [37, 38].

Regarding the appropriateness of the SEM and MDC, 19% (Japan) to 51% (Nigeria) reduction in WHODAS is clinically important [15]. This corresponds to between 4.8 and 12.97 of Igbo-WHODAS mean of 25.44. Therefore, SEM of 5.05, MDC of 13.99 and limits of agreement of -8.58 to 9.54 of Igbo-WHODAS appear suitable.

Igbo-WHODAS and its subscales correlated at least moderately (rs ≥ 0.3) with performance-based disability, self-reported back pain specific disability (Igbo-RMDQ), and pain intensity (BS-11), except for the cognition and getting along subscales. There was a weak (rs = 0.19) but statistically significant correlation between the cognition subscale of the Igbo-WHODAS and performance-based disability. There was no correlation between the getting along subscale of the Igbo-WHODAS and performance-based disability. This lack of association could be because the getting along with people subscale of the Igbo-WHODAS appears to reflect the psychosocial aspect of the biopsychosocial disability model whereas the back-performance scale measures the biomedical aspect of the biopsychosocial disability model. In contrast to the Igbo-WHODAS which fully captures the multidimensional biopsychosocial disability concept including impairments, activity limitations and participation restrictions, performance-based disability is impairment focused. Impairment represents abnormalities or loss of body structure and function and conceptualises disability at the level of the body only [1]. Impairment does not automatically imply disability, as people with impairment may not experience disability, or do so at varying levels depending on personal, physical and social barriers/facilitators in different contexts [39]. Evidence suggests that performance-based disability characterise impairment-focused biomedical variables (e.g. leg strength, leg velocity), whereas patient-reported disability represent both impairment and psychosocial aspects of disability [40]. This agrees with our findings showing the greatest correlations between Igbo-WHODAS, and its mobility, participation, and life activities subscales, with back pain specific disability (Igbo-RMDQ) and pain intensity (BS-11) which are patient-reported outcomes. Furthermore, these subscales represent the construct within back pain specific measures. Cognitive dysfunction may be less important than limitations in mobility, life activities (difficulties in performing specific actions, tasks or activities related to household activities and work/school activities) and participation (difficulties of individuals to participate in community activities within specific societies) in mobility-related disability in this population. As expected, the mobility subscale of the Igbo-WHODAS had one of the strongest correlations with the BPS which measures mobility-related disability [16]. These findings support the construct validity of the Igbo-WHODAS 2.0.

A seven-factor solution of the Igbo-WHODAS was produced similar to adaptations in European languages [37] and Chinese [38]; in contrast to the six factors in the original measure [15]. Most Igbo-WHODAS items loaded on their corresponding factor in the original measure except for participation. The participation subscale of the original WHODAS 2.0 (meant to reflect the impact of participants’ back pain on their participation in society) was the least precise with only two of the original eight items (‘drain on financial resources’ and ‘problem to family’) loading on factor 5. The other items in the original participation subscale loaded on all other factors except self-care. Differences could be due to high illiteracy resulting in high measurement error or different population characteristics, although the latter is more likely to be the case.

Factor 1 of the Igbo-WHODAS can be termed life activities, community involvement and functional independence factor as it reflects the difficulties participants may have in: performing daily household/work/school activities, joining in community activities, doing things or staying by oneself. The rural dwellers from whom the factor structure of the Igbo-WHODAS was derived were mostly involved in informal self-employed occupations within the community [12, 19, 22] which could explain why work activities, community involvement and staying/doing things for oneself loaded as one factor. Factor 2 of the Igbo-WHODAS can be retained as the getting along factor as in the original subscale. The additional loading of one item of the original participation subscale D6.3 and one item of the original cognition subscale D1.5 suggests that living with dignity due to the action of others and understanding what people say are key to people living with CLBP getting along with others in the community.

Factor 3 of the Igbo-WHODAS can be named mobility and concern factor since two additional items from the original participation subscale (time spent on back pain D6.4, and emotional effects of back pain D6.5) loaded on it. This suggests that participants are less likely to be mobile when they spend time worrying about their back pain. This concurs with qualitative results from this population showing that people with CLBP often spend time alone in bed thinking and worrying about their condition [19]. This explains why the two items ‘time spent on back pain’ and emotional effects of back pain are loaded together. The designation for factor 4 can be retained as cognition as in the original cognition subscale despite one of the original items (understanding what people say D1.5) loaded on the getting along factor. Understanding what people say may be more related to getting along with people than cognition in this population with CLBP.

Factor 5 can be termed financial impact as it had only two items (back pain drained financial resources D6.6 and back pain caused family problems D6.7), which were in the original participation subscale loading on it. Qualitative research evidence [19] from this population suggests that reduction of financial resources due to work-related disability from CLBP had a great negative effect on family relationships causing family problems as indicated by participant comments:

“…It means that you are not able to do the work that supports your existence. With that you will see that there will be no money, there will be no food until I recover and start going to work...’’ (P3, Male, aged 42 years). “…brings problems into the home...because the money isn’t enough…“(P17, Male, aged 46 years) [19].

Factor 6 is entitled self-care as in the original self-care subscale despite having one missing item (staying by yourself for a few days D3.4) that loaded on factor 1 (life activities, community involvement and functional independence factor). Notably, this item D3.4 in the original self-care subscale appears very similar to item D6.8 problem doing things by oneself for relaxation/pleasure in the original participation subscale. These concepts appear to belong to one construct and should be examined in future studies. Factor 7 can be seen as redundant as it had only one major item D6.2 (barriers and hindrances in the world around one due to back pain) from the original participation subscale. However, factor 7 had secondary loadings from two items, D6.3 (problem living with dignity due to attitudes/actions of others) and D4.2 (difficulties maintaining a friendship), both of which loaded primarily on factor 2 (getting along with people). This suggests that the barriers and hindrances that people with CLBP in rural Nigeria face in the world around them could be related to problems they have living with dignity due to attitudes/actions of others and difficulties maintaining a friendship. These findings require further exploration. Moreover, further research is required to confirm the factor structure of the Igbo-WHODAS.

The Igbo-WHODAS 2.0 did not have floor and ceiling effects. However, the floor effects observed in the cognition, self-care and getting along subscales could also mean that these are not the major domains affected in CLBP-disability in rural Nigeria where emphasis appear to be on pain intensity, mobility, work activities and participation in society [19, 22].

This study enabled the development of a valid and reliable generic measure of disability for Igbo speaking populations. This is important since non-English speaking rural Nigerians are often neglected clinically and during research despite having one of the highest disability rates. The demonstrated complexity of developing a valid and reliable measure for this population could be related to cultural, linguistic and literacy issues.

Despite acceptable validity and reliability levels, high sample variability and measurement errors were probably introduced by low literacy rates, interviewer- administration and data collection by several raters. This is important as MDC not only depends on the inherent measurement error of an instrument, but varies across populations and contexts [41, 42]. Hence, sensitivity-to-change studies of the Igbo-WHODAS 2.0 is required in populations of varying literacy levels, with single raters, and using more rigorous analysis such as receiver operating characteristic (ROC) curves, which includes patients’ own global impression of change [43]. Furthermore, these studies need to confirm the MDC of the Igbo-WHODAS, and determine the proportion of people that achieve it. Bilingual assessment of the agreement between the original WHODAS and Igbo-WHODAS 2.0, including item by item agreement in a population with adequate literacy levels to enable comprehension of the English and Igbo versions is also necessary.

The lack of rigorous investigation of item redundancy in this study can be explored in future studies. Redundancy could be demonstrated in terms of items that are too similar which spuriously inflate reliability [44], or items that are not applicable in this particular culture or population [45]. Reducing redundancy involves excluding items that are not applicable in a population following assessment by a team of content experts from a culture. Items rated by a single team member as irrelevant, or by two or more members as questionably relevant should be eliminated, whereas items obtaining one rating of questionable relevance should be reconsidered for inclusion. Re-assessment of internal consistency would then be needed when any item is removed from a measure to ensure that an acceptable Cronbach’s alpha (> 0.60) is maintained [45]. Following the elimination of redundancy, multi-group confirmatory factor analyses may be needed to compare and determine the factor structures with the best fit indices in rural Nigeria, assess if the same items assess the same construct in different populations in rural Nigeria, whether the items of a given factor are equally significant within different cultures in rural Nigeria or are too different; and if items are more biased towards some cultural groups than others. Using item response theory, items with different functioning may be eliminated so that groups are comparable, in which case the measure becomes somewhat different from the original or considered differently in separate groups to maintain equivalence between scores [44].

The acceptable internal consistency of the Igbo-WHODAS 2.0 suggest that items were sufficiently independent but were adequately similar. However, Principal Components Analysis (PCA), a data reduction technique which identifies and discards highly correlated items may be required in future studies involving the Igbo-WHODAS 2.0. As PCA is a large sample evaluation requiring at least five times the number of items in a questionnaire being analysed, a much larger sample size than the one used in this study will be required in future studies. This is more so when only a few items are expected to load onto each component, and when variable communalities (percentage of variance in an observed variable that is accounted for by the retained components) are low [46]. Furthermore, confirmatory factor analyses would require a sample size of at least 300 when there are only a few high factor loading scores (> 0.80) [47]. This should be the focus of future research.

Other strengths of this study include the validation of Igbo-WHODAS 2.0 with both self-reported and performance-based disability as well as pain intensity measures, with established correlations which are in line with the literature, supporting its validity.

The Igbo-WHODAS is valid and reliable for clinical and research purposes in Igbo speaking culture. It would support global health initiatives which often involve concurrent activities in countries of different languages and culture.

Ethics approval and consent to participate:

King’s College London (Ref: BDM/13/14–99) and University of Nigeria Teaching Hospital (Ref: UNTH/CSA/329/Vol.5) gave ethical approvals.

Consent for publication:

Not applicable.

Availability of data and materials:

Data is available on request due to ethical restrictions imposed by Biomedical & Health Sciences, Dentistry, Medicine and Natural & Mathematical Sciences Research Ethics Subcommittees (BDM RESC) Kings College London. Requests for data access may be made to BDM RESC Kings College London through email [email protected].

Competing interests:

The authors declare that they have no competing interests.

Funding:

This study was funded by the Tertiary Education Trust Fund, Nigeria and the Schlumberger Foundation, The Netherlands. Both organizations had no influence on the study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the manuscript for publication.

Authors’ contributions:

CNI-C conceived of this work, designed the study, collected data, conducted analyses, interpreted findings, and drafted the initial manuscript. ELG, IOS and SK contributed to interpretation of findings. EG and SK supervised data collection. All authors read, provided feedback and approved the final version of the manuscript to be published.

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World Health Organisation Disability Assessment Schedule (WHODAS 2.0): development and validation of the Igbo version in patients with chronic low back pain

Status:

Journal Publication

Version 1

Abstract

Background

Methods

Results

Conclusions

Figures

Introduction

Methods

Ethical concerns

Study designs

Outcome measurement tools

World Health Organisation Disability Assessment Schedule (WHODAS 2.0)

Igbo Roland Morris Disability Questionnaire (Igbo-RMDQ)

Back performance scale (BPS)

Eleven-point box scale (BS-11)

Cross-cultural adaptation process

Participants

Procedure

Psychometric testing process

Participants (sample size calculation for test-retest reliability)

Participants (sample size calculation for construct validity)

Procedure for psychometric testing

Collection and fidelity of data

Data analyses

SEM = SD √(1-R)

MDC = 1.96 * √2 * SEM

Results

Cross-cultural adaptation participants

Translation, pellucidity and cultural equivalence of Igbo-WHODAS

Psychometric properties of Igbo-WHODAS

Participants

Findings from fidelity assessment

Reliability

Construct validity

Discussion

Conclusions

Declarations

Ethics approval and consent to participate:

Funding:

Authors’ contributions:

References

Status:

Journal Publication

Version 1