Risk of tuberculosis among contacts of isoniazid-resistant and isoniazid-susceptible cases.

Tuberculosis Research Centre, Indian Council of Medical Research (ICMR), Chennai , India .

International Journal of Tuberculosis and Lung Disease; 2011; 15; 782–788.

Summary : Objective: To compare the risk to household contacts of isoniazid (INH) susceptible and INH-resistant cases of tuberculosis (TB) in a rural community in South India .

Methods: In all, 5562 contacts of INH-susceptible and 779 contacts of INH-resistant patients and 246845 persons with no TB case in the home were followed for 15 years, with surveys every 2.5 years comprising radiographic and sputum examination, selective follow-up of high-risk individuals and passive surveillance. If a new case developed, the household members were assigned to the ‘INH-susceptible' ( n = 7088) or ‘INH- resistant' series ( n = 526), whichever appropriate. Logistic regression and Cox's proportional hazards model were employed.

Results: The baseline prevalence of tuberculous infection was respectively 70% and 56% in contacts of INH-resistant and INH-susceptible patients ( P < 0.001), compared to 46% in non-contacts. The incidence of culture-positive TB was respectively 295 and 311 per 100 000, compared to 162/100 000 in non-contacts. The adjusted hazard ratios were 2.4 and 2.0 for contacts of INH-resistant and INH-susceptible patients.

Conclusion: The baseline prevalence of tuberculous infection was substantially higher in contacts of INHresistant than INH-susceptible patients, but the incidence of tuberculous disease over a 15-year follow-up was similar in the two series, and twice as high as in non-contacts.

Keywords: I nfectivity; INH-resistant TB; risk; contacts; hazard ratios

Back to List of publications / Home