Ethical considerations
Ethical approvals were obtained from King’s College London (Ref: BDM/13/14–99) and the University of Nigeria Teaching Hospital (Ref: UNTH/CSA/329/Vol.5). Written permission was obtained from the original developers of the measure.
Study designs
Translation, cultural adaptation, test-retest measurements and cross-sectional study of psychometric properties of the HADS were performed.
Outcome measures
Hospital Anxiety and Depression Scale (HADS)
The HADS (17) is a measure of anxiety and depression which have been found to play a key role in the development and maintenance of CLBP. It has two subscales for anxiety (HADS-A) and depression (HADS-D), with seven items each. Each item has scores ranging from 0 to 3. A total subscale score of 0 on either anxiety or depression subscales means there is no anxiety or depression, and 21 is the maximum possible score meaning the most severe anxiety or depression. Summing the scores of anxiety and depression reflects a score of emotional distress with 0 meaning no distress, and 42 meaning highest possible level of emotional distress. Cut-off scores are 0 to 7 for non-cases; 8 to 10 for borderline/mild cases; 11 to 21 for definite/severe cases; with a score of 11 or more indicating “potential psychiatric caseness”. The original measure reported internal consistency of 0.41–0.76 for anxiety, and 0.30–0.60 for depression (17). Changes of 1.32–1.68 have been reported as clinically important (28).
Igbo Roland Morris Disability Questionnaire (Igbo-RMDQ)
The RMDQ is the most commonly used valid measure of LBP disability (29). It is a core outcome measure for LBP clinical trials, meta-analyses, cost-effectiveness analyses and multicenter studies. RMDQ is simple to administer, easily understood, and is the best measure for population or primary care-based studies (30). The Igbo-RMDQ (31) was cross-culturally adapted from the original English version (32). It is a twenty-four item back specific self-report measure with each item having possible scores of 0 or 1. A total maximum score of 24 denotes the highest possible disability level and 0 means no disability. It has good face and content validity, construct validity, internal consistency, test-retest reliability and responsiveness (33). The Igbo-RMDQ has Cronbach’s alpha of 0.91; test-retest reliability of 0.84; and a 2-3-point change from baseline is considered clinically important.
Igbo World Health Organisation Disability Assessment Schedule (Igbo-WHODAS 2.0)
The WHODAS 2.0 is a comprehensive measure of disability, with an interviewer-administered version that measures disability within the International Classification of Functioning Disability and Health (ICF) biopsychosocial model (34). It emphasizes all six domains of disability (cognition, mobility, self-care, getting along with people, life activities and participation), and includes work-related disability. Nigeria was one of the 21 countries that contributed data for its development, supporting its cultural sensitivity in Nigeria. As the measure is generic and comprehensive, it would enable comparisons across populations, conditions and an understanding of the disability domains affected. The Igbo-WHODAS 2.0 (35) was adapted from the original English version (36), and has good face and content validity, construct validity, internal consistency, test-retest reliability and responsiveness. It has Cronbach’s alpha ranging between 0.8 and 0.9; test-retest reliability ranging between 0.8 and 0.9; and minimal detectable change ranging between 13.99 and 30.77.
Due to the low literacy levels in this population, the 36-item interviewer-administered version was used using the complex scoring method which takes into consideration multiple levels of difficulty for each WHODAS 2.0 item. This involved 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) (36).
Igbo Fear Avoidance Beliefs Questionnaire (Igbo-FABQ)
The FABQ (37) is one of the best measures for assessing fear avoidance beliefs. It is a sixteen-item back pain-specific self-report measure that assesses the extent to which pain is believed to be caused or aggravated by general physical activity (FABQ-PA) and work-related activities (FABQ-W). These represent the two subscales of the measure. FABQ-PA has five items, each scored with a Likert scale ranging from 0 (completely disagree) to 6 (completely agree). One item [1] is a distractor and is not scored. The maximum score for FABQ-PA is 24 and the minimum is 0, with higher scores indicating stronger fear avoidance beliefs related to physical activity. FABQ-W has 11 items, each having a Likert scale ranging from 0 (completely disagree) to 6 (completely agree), but four items [8, 13, 14, 16] are distractors, and do not contribute to total score. The maximum score for FABQ-W is 42 and minimum score is 0, with higher scores indicating stronger fear avoidance beliefs related to work activities. Summing the two subscale scores gives a total FABQ score of 64, with higher scores reflecting stronger fear avoidance beliefs. The original FABQ correlates significantly with other measures of fear-avoidance such as the Tampa Scale of Kinesiophobia; r = 0.33–0.59 (38) and a change of 13 from baseline is reported to be clinically important (39). The Igbo-FABQ was developed from the original English FABQ (40), and has good internal consistency (α = 0.80–0.86); intra class correlation coefficients (ICC = 0.71–0.72); standard error of measurements (3.21–7.40) and minimal detectable change (8.90–20.51).
Eleven-point box scale (BS-11)
BS-11 is a single item eleven-point numeric scale for pain intensity. It consists of eleven numbers (0 through 10) surrounded by boxes (41). Zero represents ‘no pain’ and 10 represents ‘pain as bad as you can imagine’ or ‘worst pain imaginable’. It has good psychometric properties including high test–retest reliability in both literate and illiterate patients with rheumatoid arthritis (ICC = 0.96 and 0.95). It was easier to comprehend and administer than the visual analogue scale (VAS) in this population (15,42). The measure is highly correlated (0.86–0.95) with the VAS in patients with rheumatic and other chronic pain conditions; and a reduction of 2 points is regarded as clinically important (43).
Cross-cultural adaptation process
Participants
A health psychologist (native Igbo speaker; bilingual in English and Igbo) who had practised for 9 years in Nigeria and three non-clinical translators (one native Igbo speaker who was bilingual in Igbo and English; one native English speaker who was bilingual in English and Igbo; and one English/Igbo linguistic expert) made up the translation team. An expert review committee included two English experts (health psychologist and academic physiotherapist) working in the United Kingdom, and two Igbo experts (clinical psychologist and clinical physiotherapist) working in Nigeria.
Pre-testing/piloting of the Igbo-HADS was done with a convenience sample of adults living with CLBP in rural Nigeria who had participated in a previous study (15). Informed consent was obtained for this study prior to data collection.
Procedure
Original English version of the HADS was cross-culturally adapted following evidence-based guidelines (44) (Fig. 1).
The questionnaires were forward translated independently from English to Igbo by one bilingual health psychologist and one bilingual translator from a non-clinical background. Both were native Igbo speakers, bilingual in Igbo and English. The items were explained to the health psychologist only. This produced two Igbo versions: T1 and T2 respectively.
T1 and T2 were synthesized via discussion between the two forward translators, mediated by the lead author who is bilingual in English and Igbo. This produced one Igbo version: T-12. Translations were compared and discrepancies were noted.
The Igbo (T-12) versions of the HADS were back translated from Igbo to English by two back translators, blind to the HADS and the construct it measures, who were from non-clinical backgrounds. One of the back translators was an English/Igbo linguistic expert proficient in the professional translation of tools, and the other was a native English speaker, born in England to
Nigerian-born Igbo parents. This produced two back-translated English versions: BT1 and BT2. This is a validation process ensuring that the translation was consistent, and that the translated (T-12) versions of the HADS were reflecting the meaning in the original HADS.
T1, T2, T-12, BT1 and BT2 were discussed by the expert committee to produce a pre-final Igbo version of the HADS. The main purpose of this committee was to achieve cross-cultural equivalence in terms of semantic, idiomatic, experiential and conceptual equivalence. For semantic equivalence, the committee explored Igbo and English words to assess if they meant the same thing, if there were multiple meanings to an item, and if there were any grammatical difficulties in the translations. Idiomatic equivalence was assured by the committee formulating alternative Igbo idioms and colloquialisms, where the English versions were difficult to translate.
For example, ‘butterflies in the stomach’, an English idiomatic expression for feeling nervous, has a different Igbo equivalent ‘my breathing flying out of my stomach’. Experiential equivalence was achieved by the committee ensuring that questionnaire items were experienced similarly in English and Igbo cultures. For conceptual equivalence, the committee determined that words in the items, instructions, and response options had similar conceptual meanings in Igbo and English cultures. The expert committee also ensured that Igbo wordings were simple and could be easily understood regardless of age and educational levels.
Finally, pre-final Igbo version of the HADS was field tested in rural Nigeria, among twelve participants living with CLBP, who had participated in a qualitative study (15). The lead author interviewer-administered the HADS using the ‘think-aloud’ cognitive interviewing procedure. Each item was read out, and participants actively verbalised their thoughts as they attempted to answer each question. Participants stated if they encountered difficulty comprehending the items, what was understood by each item, and the meaning of the chosen response. They were encouraged to keep talking while the lead author recorded their responses. This stage ensured that equivalence was achieved in the Nigerian setting to produce the final Igbo-HADS, confirming face and content validity.
Psychometric testing process
Participants
Participants for test-retest reliability
Sample size was determined a priori. A minimum sample size of 27 was required to detect an intra-class correlation coefficient of 0.9 and a maximum width of 0.23 for a 95% confidence interval (45). For test-retest reliability assessment, a convenience sample of 50 participants with CLBP, between the ages of 18 and 69 years, were recruited from rural and urban communities in Enugu State, South-eastern Nigeria. Community announcements were made in the urban community within which the University of Nigeria Teaching Hospital (UNTH), Enugu is situated and a rural community – Akegbugwu, situated close to it, inviting people with CLBP who were interested in participating in the study to meet at specific community centres. Informed consent was obtained and screening was conducted prior to data collection.
Participants for construct validity investigation
Sample size was also determined a priori. For exploratory and confirmatory factor analysis, a sample size of 200 is deemed sufficient (46). For correlation analyses, a medium Pearson correlation coefficient of 0.30, at alpha level of 0.05, and 95% power, will require a minimum sample size of 138. Hence, validity assessments were done with a representative random sample of 200 participants living with CLBP in rural communities of Enugu State.
The detailed description of participant sampling and the selection for the cross-sectional validity sample is published elsewhere (42). Multistage cluster sampling was used to select ten rural communities, representative of rural populations in Enugu State. Data were collected from 20 randomly selected participants from households in each local government area, making a total of 200 participants with non-specific CLBP (without underlying serious pathology, radiculopathy or spinal stenosis). Informed consent was obtained and screening was conducted prior to data collection.
Procedure
A training manual was produced based on the World Health Organisation Disability Assessment Schedule 2.0 manual (36), the foundations of good survey design, instructions by the developers of HADS, literature review, and verbal pretesting of Igbo-HADSs. Using the manual, ten community health workers (CHWs) were trained for two weeks in a classroom at the University of Nigeria Teaching Hospital Enugu, Nigeria, for interviewer-administration of the measures. A representative sample of the population was ensured through multistage cluster sampling. Attempts were made to recruit equal number of males and females through gender stratification. All measures were validated, and the CHWs’ training was tailored to administer the questionnaire items exactly as they were, and to avoid asking questionnaire items in ways that could bias participants’ responses. The CHWs were also trained to ensure that all recruited participants were assessed, and that no items or scales were unanswered.
Data collection
An outcome measure booklet containing screening and demographic questions, and all the questionnaires was used by each CHW to collect data. Participants were screened first by asking simple questions to rule out back pain associated with underlying serious pathology, radiculopathy or spinal stenosis. They were then requested to describe their pain location with a body chart, before the CHWs interviewer-administered the measures. Likert scales were presented to participants as ‘flash cards’ as each item was read out.
To assess test-retest reliability, the Igbo-HADS was completed at baseline and repeated seven to ten days after. The same CHW collected data from each participant on the two occasions.
For validity assessment, the Igbo-HADS was completed at one time in a cross-sectional design.
Statistical analyses
IBM SPSS version 22 was used for data analyses. Data were assessed for normality using visual (normal distribution curve and Q-Q plot), and statistical methods (Kolmogorov-Smirnov, Shapiro-Wilk’s test and Skewness/Kurtosis scores).
Reliability
Reliability investigates the ability of an instrument to measure consistently (47). Internal consistency was calculated using Cronbach’s alpha, and was rated as low/weak (0-0.2), moderate (0.3–0.6) and strong (0.7-1.0) (47).
For test-retest reliability, intra-class correlation coefficient (ICC) was calculated using a two-way mixed-effect analysis of variance model with interaction for the absolute agreement between single scores. Random effects model was preferred because of the need to generalize to different raters, and since the retest was performed after a fixed number of days, generalisation to other time points was not required (48). 0.7, 0.8 and 0.9 represented good, very good and excellent ICCs (49,50).
Bland-Altman plots were also used to visually assess the level of agreement between test-retest measurements by plotting mean scores against difference in total scores. Bland-Altman analysis accounted for the weakness of ICC which might indicate strong correlations between two measurements with minimal agreement.
Reliability was also evaluated using the standard error of measurement (SEM) and minimal detectable change (MDC). MDC is a statistical estimate of the smallest change detected by a measure that corresponds to a noticeable change in ability which is not due to measurement error. MDC was calculated using the SEM which is based on the distribution method, and the reliability of the measure which takes precision into account). SEM was based on the standard deviation (SD) of the sample and the test-retest reliability (R) of the measure, and was calculated with the equation below (51):
SEM = SD √(1-R)
MDC was subsequently calculated with the equation below:
MDC = 1.96 * √2 * SEM
1.96: 95% confidence interval of no change; √2: because two measurements are involved in measuring change.
Validity
Validity assesses the extent to which an instrument measures what it is intended to measure. As there are no ‘’gold standard’’ measures for the Igbo-HADS, construct validity was investigated. Construct validity was investigated using Pearson’s correlation (parametric data) analyses with the Igbo versions of Roland Morris Disability Questionnaire (Igbo-RMDQ), World Health Organisation Disability Assessment Schedule (Igbo-WHODAS), Fear Avoidance Beliefs Questionnaire (Igbo-FABQ) and the eleven-point box scale of pain intensity (BS-11); and were rated as weak (0-0.2), moderate (0.3–0.6), and strong (0.7-1.0) (52).
A priori hypotheses were set. Igbo-HADS is expected to have at least a moderate correlation with Igbo-BS-11 as the literature shows that anxiety and depression are at least moderately correlated with pain intensity (53–55). Anxiety and depression are also moderately associated with back-pain specific and generic disability, and fear avoidance beliefs (4,5,7,56). Hence, Igbo-HADS is also expected to have moderate correlations with Igbo-RMDQ, Igbo-WHODAS, and Igbo-FABQ.
Exploratory factor analyses (EFA) was used to determine the number of factors influencing the Igbo-HADS, i.e. the dimensionality of the Igbo-HADS (46). EFA was applied according to Kaiser Meyer Olkin (KMO) and the Bartlett’s test with a minimum eigenvalue for retention set at ⩾1.0 (Kaiser’s rule) (57). 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 as recommended (46). Extraction was done using principal axis factoring. The number of factors and the underlying relationships between the items were then compared with the factor structures of the original measures to enhance an understanding of population characteristics. Furthermore, confirmatory factor analysis was conducted to determine the model fit indices for the observed structure found the EFA in this study; and the two-factor structure found in the original measure, as well as the one-factor structure reported in the literature (58,59). Good fit indices were regarded as a Comparative Fit Index (CFI) of ≥ 0.90; a Tucker-Lewis Index (TLI), Non-Normed Fit Index (NNFI), and Normed Fit Index (NFI) of ≥ 0.95; Root Mean Square Error of Approximation (RMSEA) and Standardised Root Mean square Residual (SRMR) of < 0.08 (60,61).