Incidence and prevalence of tuberculosis among household contacts of pulmonary tuberculosis patients in a peri-urban population of South Delhi, India

Abstract

Background: Tuberculosis (TB), caused by Mycobacterium tuberculosis, is one of the leading causes of mortality and morbidity across all age groups throughout the world, especially in developing countries.

Methodology/principal findings: In this study, we have included 432 open index cases with their 1608 household contacts in a prospective cohort study conducted from May 2007 to March 2009. The follow-up period was 2 years. All Index cases were diagnosed on the basis of suggestive signs and symptoms and sputum being AFB positive. Among the 432 index patients, 250 (57.9%) were males and 182 (42.1%) females; with mean age of 34 ± 14.4 yr and 26 ± 11.1 yr, respectively. Out of 1608 household contacts, 866 (53.9%) were males and 742 (46.1%) females; with mean age of 26.5 ± 15.8 and 26.5 ± 16.0 yr, respectively. Of the total 432 households, 304 (70.4%) had ≤ 4 members and 128 (29.6%) had ≥ 5 members. The median size of the family was four. Of the 1608 contacts, 1206 were able to provide sputum samples, of whom 83 (6.9%) were found MTB culture positive. Household contacts belonging to adult age group were predominantly (74, 89.2%) infected as compared to the children (9, 10.8%). On screening the contact relationship status with index patients, 52 (62.7%) were first-degree relatives, 18 (34.6%) second-degree relatives and 12 (14.5%) spouses who got infected from their respective index patients. Co-prevalent and incident tuberculosis was found in 52 (4.3%) and 31 (2.6%) contacts, respectively. In incident cases, the diagnosis could be made between 4 to 24 months of follow-up, after their baseline evaluation.

Conclusion: Active household contact investigation is a powerful tool to detect and treat tuberculosis at early stages and the only method to control TB in high-TB-burden countries.

Figure 1. Flow chart showing details of recruitment of subjects and their follow up at every four months.

Figure 2. Map of South Delhi DOTS Centers and their surrounding areas from where all the index cases and their household contacts were recruited.

Figure 3. Time to positivity (TTP) in liquid cultures and its correlation with smear positivity.

Figure 4. Time of detecting co-prevalent (Cp) and incident (Ip) secondary tuberculosis cases.

Figure 5. Receiver Operating Characteristic (ROC) curves for Co-prevalent (a) and Incident TB (b) cases.