Progress in the second year of patients with quiescent pulmonary tuberculosis after a year of domiciliary chemotherapy, and influence of further chemotherapy on the relapse rate.

This study from the Tuberculosis Chemotherapy Centre, Madras, summarizes the progress during the second year of those patients in a 1-year comparison of four domiciliary chemotherapeutic regimens (isoniazid plus PAS and three regimens of isoniazid alone) whose pulmonary tuberculosis had attained bacteriological quiescence at the end of the year of chemotherapy. During the second year, about half of the patients received further chemotherapy, with isoniazid alone, and the remainder received a placebo, calcium gluconate. The main objects of the study were to determine the influence on the progress during the second year of (a) a second year of chemotherapy with isoniazid alone, (b) residual cavitation at the end of the first year, and (c) the chemotherapeutic regimen received during the first year, and to compare the results with those obtained in an earlier study by the Centre of the progress during the second year of patients with quiescent pulmonary tuberculosis after a year's chemotherapy with isoniazid plus PAS at home or in sanatorium.The results of the present study, which was planned on the same lines as the earlier one, showed that relapse in the second year was unrelated to the chemotherapeutic regimen received in the first year, and it was therefore permissible to amalgamate the findings in the two studies. The amalgamated results showed that the relapse rate in the second year was low (5.9%) and that a second year of treatment with isoniazid alone was of definite value for the patients with no residual cavitation at the end of the first year, but had no effect on the relapse rate of those with residual cavitation. The combined data from the two studies have thus clarified the position with regard to the effectiveness of isoniazid in preventing bacteriological relapse in patients without residual cavitation, slight evidence of which was apparent in the earlier study.