Trends in the prevalence of Pulmonary Tuberculosis over a period of seven and half years in a rural community in south India with DOTS.

Setting: Tiruvallur district In Tamil Nadu where DOTS was implemented by the State Government as the tuberculosis control measure in 1999, and monitored by the National Institute for Research in Tuberculosis for over five years. Objective: To estimate trends in TB prevalence in a rural community with DOTS. Design: Surveys of pulmonary tuberculosis were undertaken in representative samples of subjects aged >15 years (N = 83,000 – 92,000), initially and after two and half, five and seven and half years of implementation of DOTS. Sputa were collected from those with abnormal radiograph and/or presence of chest symptoms, and examined by direct smear and culture. Results: The prevalence of culture-positive tuberculosis was 607, 454, 309 and 388 per 100,000 in the four surveys, and that of smear-positive tuberculosis was 326, 259, 168 and 180. In the first five years; annual decrease was 12.4% (95% CI 10.4 - 14.4%) for culture-positive tuberculosis, and 12.2% (95% CI 8.0–16.2) for smear-positive tuberculosis. This was, however, followed by a significant increase in the next two and half years. The average new smear-positive case-notification rate was 75 per 100,000 during first four years but declined to 49 in subsequent years. There were no methodological differences during this period and information on changes in socio-economic indicators and nutritional standards was unavailable. Conclusion: Despite the average annual success rate (78%) in this tuberculosis unit being lower than the expected rate of 85%, the implementation of DOTS was followed by a substantial decrease in the prevalence of pulmonary tuberculosis over the seven and half year period. Our findings suggest that sustaining the high effectiveness of DOTS programme needs vigilant supervision.

Comparison of tuberculin reaction sizes at 48 and 72 hours among children in Tiruvallur district, south India.

SETTING: A rural population in Tiruvallur district, south India. OBJECTIVE: To study the variability of skin test reaction sizes between 48 and 72 hours. METHODS: A tuberculin test survey was conducted among children aged less than 10 years. The reaction sizes were read by the same reader at 48 hours and 72 hours independently. The results of the tuberculin test were compared. RESULTS: Of 957 children aged below 10 years were included in the study; the male and female ratio was 1: 1.1. There were no significant differences between the readings of reaction size at 48 and 72 hours. CONCLUSION: The tuberculin test results can be read either at 48 hours or 72 hours without compromising the validity.

Estimation of annual risk of tuberculosis infection among children irrespective of BCG scar in the south zone of India.

Objective: To estimate the proportion infected and compute Annual Risk of Tuberculosis Infection (ARTI) among children irrespective of BCG scar and compare with that among children without BCG scar. Methodology: Tuberculin survey was conducted in south zone of India as a part of the nation-wide survey to estimate the ARTI in different parts of the country and ARTI was computed among children without BCG scar excluding children with BCG scar. In this exercise, the tuberculin test results of children with BCG scar and irrespective of BCG scar were considered for analysis and the results were compared. Results: The prevalence of infection and ARTI estimated among children irrespective of BCG scar aged 1-9 years were 5.7% and 1.0% (95% C.I: 0.8-1.3) respectively. The corresponding figures among unvaccinated children were 5.9% and 1.0% (95% C.I: 0.7-1.4) respectively. The ARTI among children irrespective of BCG scar were similar to that among unvaccinated children. Conclusion: Estimation of proportion of children infected and computation of ARTI using mirror-image technique could be undertaken among children irrespective of BCG scar among children aged either from 1-9 years or 5-9 years.

Estimation of burden of tuberculosis in India for the year 2000.

BACKGROUND AND OBJECTIVE: Data on the burden of tuberculosis (TB) in India are vital for programme planners to plan the resource requirements and for monitoring the nation-wide TB control programme. There was a need to revise the earlier estimate on the burden of TB in India based on the increase in population and current epidemiological data. This study estimates the burden of disease for the year 2000 based on recent prevalence of TB and annual risk of tuberculosis infection (ARTI) estimates. METHODS: Data on prevalence generated among adults by the Tuberculosis Research Centre (TRC), Chennai, among children by National Tuberculosis Institute (NTI), Bangalore, and the ARTI estimates from the nation-wide sample survey by NTI and TRC were used for the estimation. The prevalence of disease corresponding to 1 per cent ARTI was extrapolated to different parts of the country using the estimates of ARTI and the population in those areas and added together to get the total cases. Abacillary cases that required treatment were estimated from X-ray abnormals. The estimates of bacillary, abacillary and extrapulmonary cases were then combined to get the national burden. RESULTS: The estimated number of bacillary cases was 3.8 million (95% CI: 2.8-4.7). The number of abacillary cases was estimated to be 3.9 million and that for extrapulmonary cases was 0.8 million giving a total burden of 8.5 million (95% CI: 6.3-10.4) for 2000. INTERPRETATION AND CONCLUSION: The present estimate differs from the earlier estimates because we have included the disease burden of X-ray cases that are likely to breakdown to bacillary cases in a one year period, and extrapulmonary TB cases. The current estimates provided baseline information for advocacy and planning resource allocation for TB control activities. Also, these estimates can be compared with that in future years to measure the long term impact of TB control activities in India.