The effect of specific anti TB drugs on patients having smear negative radiologically positive pulmonary tuberculosis (suspect cases), was studied in Lady Willingdon Tuberculosis Demonstration & Training Centre (LWTDTC), Bangalore during 1975 & 1976. The main objective was to know the proportion of suspect cases treated under the programme requiring the specific treatment with anti TB drugs. A total of 457 suspect cases were randomly allocated to one of the two regimens; 228 patients were treated with INH + Thioacetazone (TH) and 229 with calcium gluconate (Placebo) regimens, for one year. The placebo group allowed a concurrent comparison of status of suspect cases without any specific treatment. After the intake, sputum examination by direct smear, culture for M.tuberculosis and sensitivity for drugs as well as X-ray examinations were carried out at 0, 2nd, 4th, 6th, 9th and 12th month of treatment.

Among the 228 patients on TH, 103 (45.2%) were real suspect cases, 83 (36.4%) sputum positive and remaining 42 non- tubercular. Similarly, out of the 229 patients on placebo regimen, 110 (48%) were real suspect cases, 61 (26.5%) sputum positive and 58 non- tubercular. The effect of treatment was measured by observing the incidence of bacteriologically positive or radiologically active disease from among the real suspect cases of the two groups. At the end of the treatment period, 12.6% of TH group and 29.7% of placebo group were broken down, the difference being statistically significant. Further, an element of self healing was also observed, as about 40% of patients in placebo group showed either clearance of lesions or continuing regression which could be due to self healing or the lesion being non- tubercular in nature. About 30% of the 457 patients at the start of the study were real cases of tuberculosis who under the programme were missed and 20% broke down with bacteriological positive or progress to radiologically active disease when treatment was not offered. Thus, nearly 50% of the suspect cases diagnosed in the programme required anti TB treatment and for those requiring treatment, perhaps TH is not sufficient, as 12.6% broke down in spite of treatment. It would be appropriate to treat suspect cases both from the clinical and epidemiological point of view after taking due precautions to remove non- tubercular cases by doing repeat sputum examination.