The strategy to end tuberculosis by 2030 pursues goals such as a 90% reduction in mortality and an 80% reduction in disease incidence(24). To achieve these goals, diagnosis and treatment of patients has an important role to play, which also requires an optimal Surveillance (21). In routine smear positive pulmonary tuberculosis surveillance system in the study area in 2016, the incidence rate was 9.8 / 100,000, but in the present study after collecting data from three sources and eliminating duplicates, the incidence rate was 10.3/100,000 people. The number of differences in cases were 6 patients, and after the study it was found that 4 (66%) of these patients were not included in the TB treatment system because they had died in the early days of diagnosis and treatment in the hospital. This point has been mentioned in a number of studies(25). This can have an impact on the indicators of the Surveillance, 3% in reducing the success rate of treatment and equally in increasing Mortality rate from disease. Using the linear logarithm model - a model that includes the independent effect of each source - the number of cases not recorded in any of the sources was estimated to be 19, which is consistent with the results of the Dunbar et al. Study in South Africa(17). Based on the results of this study, the completeness of reporting smear positive pulmonary tuberculosis in Ahvaz city using the data of three sources of hospital, laboratory and physician reporting was 87.5%, which is similar to the results of studies in France and Romania (12, 26) And the World Health Organization's Executive Task Force on Tuberculosis Control, which provides for the detection of at least 70% of Positive smear tuberculosis cases(17). The highest percentage of completeness of reporting (79%) was related to laboratory data, which was consistent with Vanina Guernier's study in France, Cojocaru study in Romania, and Ibarz-Pavon study in Greece(12, 13, 26).
According to a 2016 World Health Organization report, the estimated incidence of all forms of tuberculosis in Iran is estimated at 16 per one hundred thousand (27)and Therefore, considering the ratio between different forms of tuberculosis, the incidence estimated by this organization is lower than the rate calculated in this study. It should be noted, however, that this estimate is for the entire population of Iran, while the incidence and prevalence of tuberculosis is high in the marginal areas of Iran including Khuzestan province (28). The assumptions of Capture recapture studies, such as population closure, the possibility of finding commonality between sources, the independence of resources from each other, and the dependence of the catch on the specificity of the individuals at the time of these studies should be considered (17). In this study, due to the use of Excel software and sort data by name, surname and national code and manual review of all records, the default breach is that it is limited to find commonality between resources. The study also included a population closure assumption and included only patients who resided in the study area, but because this city is the center of the province, some patients may have mentioned their relatives’ address at the time of hospitalization and so were included in the study. The default breach of catch dependency regarding individuals’ characteristics is limited due to the widespread use of primary health care at the county level and the free diagnosis and treatment of tuberculosis.
In Capture recapture studies, by including the interaction between different sources, the effect of dependence (positive or negative) between the sources can be taken into account in the estimates and the bias due to the lack of default independence of resources can be largely eliminated (29).
In this study, the elimination of duplicates prevented overestimation and since only those with laboratory confirmation were included in the study, the accurate default of diagnosis was considered and no false positives remained in the data.
Gong et al in 2015 studied the treatment adherence among sputum smear-positive pulmonary tuberculosis patients in Xinjiang, China (30). They result showed that among 8289 patients, 3827 men (84.4% of male patients) and 3220 women (85.7% of female patients) had good adherence during treatment follow-up. 1242 patients (15.0%) did not complete regular follow-up. 332 (4.0%) patients lost contact (30).
In another study, Smit et al estimate the completeness of notification of incident tuberculosis cases in the Netherlands (3). They reported that between 1499 tuberculosis patients which were identified, of whom 1298 were notified, resulting in an observed under-notification of 13·4% (3). Also, prediction by Log-linear capture–recapture analysis initially a total number of 2053 (95% CI 1871–2443) tuberculosis cases (3). Huseynova et al in Iraq studied on tuberculosis burden and reporting in resource-limited countries (15). Based on result this study A total of 1985 TB cases registered 1677 patients (observed completeness 84%). They investigated total number of TB cases was 2460 (95%CI 2381–2553), with identified TB cases representing 81% (95%CI 69–89) (15). Huseynova et al administrated that TB surveillance needs to be strengthened to reduce under-reporting.
In Egypt by Bassili et al evaluation of tuberculosis case detection rate in resource-limited countries (5). According result this study CDR of NTP surveillance and completeness of case ascertainment after record linkage was respectively 55% (95%CI 46–68) and 62% (95%CI 52–77). They stated that sputum smear-positive TB cases, these proportions were 66% (95%CI 55–75) and 72% (95%CI 60–82), respectively (5).
In the three-source capture analysis, data collected from each source should be more than 15% of the total catch and have sufficient overlap(17). In the present study, data from laboratory, hospital, and physician reporting sources dedicated 90%, 34%, and 18% of all cases of disease, respectively to themselves. The highest overlap was between the laboratory and hospital sources and the lowest overlap was between hospital source and physician reporting which were inconsistent with the results of the study by Dunbar et al(17). It is suggested to report the disease from the hospital and laboratory level using electronic systems in order to eliminate the challenge of not registering patients in the TB treatment system and in view of strengthening the approach of electronic medical records in recent years. In addition, the cases of tuberculosis admitted to hospital can be seasonally extracted and compared with reported cases by examining the hospital registration system. Continuous evaluation of the disease care system using the, capture recapture method is also recommended.