The incidence rates of sputum positive pulmonary tuberculosis (cases) from the five year follow ups of a rural population done by National Tuberculosis Institute were reported on the basis of studies at intervals of one and a half to two years. Information on fate of cases was also likewise reported. These parameters appear to be imprecise since incidence and fate of cases at shorter intervals were not taken into account. Thus, the information on incidence of pulmonary tuberculosis in India is meager as compared to that on prevalence of disease. Therefore, a study mainly to find out the incidence and fate of cases at shorter intervals of 3-6 months was undertaken in 87 randomly selected villages of Nelamangala sub-division, Bangalore district which was one of the 3 sub-divisions where repeated epidemiological surveys had been conducted between 1961-68. The sample of villages in the present investigation was other than that included in the earlier report. Organized Case-finding, anti-tuberculosis treatment and BCG vaccination neither existed nor could be provided in the area till the completion of the study. The present study was conducted between 1968-1972.

This study conducted among 30,576 persons has shown that incidence of cases over a period of three months was 0.99 per thousand and was not much different from the annual rate of 1.03 per thousand reported on the basis of repeated surveys at longer intervals. That the three months rates were not a quarter of the annual rates meant that the procedure of calculating incidence rates on the basis of surveys done at varying intervals after adjusting for the interval had to be used with great caution. The study of fate of cases showed that cases converted or reverted even at shorter intervals and this appeared to be going on continually in the community. However, incidence of cases and cure and death from among the existing as well as the fresh cases kept on balancing each other so that the prevalence rates of cases studied at shorter or at longer intervals did not show variations.

A study was conducted to augment Case-finding in the programme by increasing case yield through repeated sputum examinations by collecting 2-3 samples on the same day. The study was conducted in nine Peripheral Health Institutions (PHIs) of Bangalore district. They were all Microscopy Centres and were drawn on the basis of random allocation. A Health Visitor (HV), Laboratory Technician and Laboratory Attendants of National TB Institute (NTI) were posted at the PHIs during the entire study period. After collection of first sputum sample from the eligible chest symptomatics, 2nd, 3rd or 4th samples were collected at an interval of half an hour from those whose first specimen was negative. Separate smears were prepared from all the specimens for examination at NTI. The duration of the study was nine months.

From among 4233 total new outpatients, 458 chest symptomatics were identified. Of them, 451 gave the first specimen, 416 the second specimen and 379 and 332 the 3rd and 4th specimen respectively. There were a total of 25 smear positive cases; 18 were detected by the first specimen, 3 were added by second and the remaining 4 by the 4th specimen. Of the 451 chest symptomatics, 185 were selected by the PHI Medical Officers (MOs) and 266 were picked up by the NTI HVs from the remaining outpatients. Of the 25 cases detected, 10 came from the chest symptomatics selected by the MOs and 15 came from those selected by the NTI HV. The study has shown the feasibility of collecting multiple specimens of sputum from each symptomatic on the same day. A loss of 60% cases was due to casual symptom questioning by the MOs. It was further observed that the intensity of the physical suffering has influenced the behaviour of patients towards action taking. The sputum positivity rate was 5.5%