Estimation of the Prevalence of Latent Tuberculosis Infection among Household contacts of Sputum Culture Positive Tuberculosis Patients in Vellore, South India.

INTRODUCTION : Tuberculosis still remains a major public health problem despite the fact that the causative organism Was discovered some 100 years back and highly effective drugs are available for its treatment. Worldwide 9.1 million cases are detected annually out of which half are sputum positive .1 South East Asia which account for 25% of the world’s population accounts for 34% of world’s Tuberculosis burden . WHO has identified 22 high burden countries in terms of tuberculosis incidence which account For 80% of global tuberculosis burden. India ranks 17th among 22 high burden countries in terms of tuberculosis incidence rate.1 India is The country with the highest burden of tuberculosis in the world accounting for 1/8th of the global Incidence of tuberculosis.2 Annually, around 1.9 million cases of tuberculosis are detected in India out Of which 0.8 million are sputum positive infectious cases. In India, everyday more than 5000 people develop tuberculosis disease and nearly 1000 die due To tuberculosis i.e. 2 deaths every 3 minutes.2 Deaths due to tuberculosis exceed the combined deaths Due to all other communicable diseases and account for 26% of all avoidable deaths in adults.2 Tuberculosis affects the most productive age group. Of all tuberculosis cases in India 2/3rd are Male and 70% of all patients are aged between 15 and 54 years.3 More than 3,00,000 children are Forced to leave school because their parents have tuberculosis and about 1,00,000 women with Tuberculosis are rejected by their families annually. OBJECTIVES : 1. To estimate the prevalence of latent tuberculosis infection in the household contacts of sputum Culture positive tuberculosis patients among suspected multi drug resistant tuberculosis patients In a population covered by CHAD Tuberculosis Unit and District Tuberculosis Centre TB Unit In Vellore district using tuberculin skin testing (TST) and whole blood interferon gamma (i.e. Quantiferon TB –Gold). 2. To find the agreement between Quantiferon TB-Gold and TST in detecting latent tuberculosis Infection in the above population. JUSTIFICATION : The status of the disease and disease trends is one of the basic requirements in the development of control programme for that disease and its subsequent evaluation. Subjects in contact with infective pulmonary tuberculosis may be infected if the index case coughs and expels Mycobacteria into the air. Infected contacts will then develop a progressive immune response and some (between 5-10% of those who are exposed) will develop tuberculosis disease within their lifespan. This progression from infection to disease will depend on several factors , such as age, sex, size of tuberculin reaction, immune status, diabetes, smoking, drug treatment and nutritional status. The risk of developing tuberculosis disease from tuberculosis infection is maximum in the first 2 years following infection and decreases with time. SUMMARY : A cross sectional study was undertaken among the household contacts of sputum culture positive tuberculosis patients among suspected MDR cases in Vellore, South India. Among a total of 147 suspected MDR cases who underwent sputum culture testing, 104 were found culture positive. Of these 44 household were contacted and 40 household agreed to participate in the study. In these 44 household , 154 household contacts were screened. Valid results were available for 150 individuals only. Of 150 for whom valid results are available, 120(80%), were found to be positive for latent tuberculosis infection by TST and 63.3% by QFT. This showed a high prevalence of latent tuberculosis infection among household contacts of infectious tuberculosis patients who are suspected to have MDR TB. In high burden, resource limited countries like India, the TST might still serve a useful purpose. In India, a 15-year follow up of 2,80,000 individuals showed that TST response is significantly associated with development of active tuberculosis.8 In India, TST is widely used in diagnosing childhood tuberculosis and in epidemiological studies to estimate annul risk of tuberculosis infection