[Impact of introducing rifampicin for the treatment of tuberculosis during the 1970's in Japan].

Setting: The average duration of tuberculosis chemotherapy in Japan increased year by year throughout the 1960's and reached 49 months by 1973. It then began decreasing slowly in the 1970's and more rapidly after the 1980's.

Purpose: To clarify the significant factors contributing to the prefectural variation of changes in the average duration of chemotherapy that occurred from 1973 to 1979.

Method: Multiple regression analysis was conducted with the slopes of the average duration of chemotherapy of tuberculosis in prefectures throughout Japan from 1973 through 1979 as the dependent variable and with parameters related to treatment and patient characteristics of the prefectures as independent variables.

Results: The variables, including uses of rifampicin, proportion of bacteriologically confirmed patients among newly registered cases, and average duration of chemotherapy as of 1973, contributed significantly to the slope of change in chemotherapy duration of the prefectures; the duration decreased faster in prefectures where there were more bacteriologically confirmed patients, and where the duration had been shorter at the beginning of the study period.

Discussion: Short-course chemotherapy had not been established in the study period, but confidence in the potency of antibacterial activity of the new drug seems to have facilitated the departure from unnecessarily long treatment. The recognition of the importance of bacteriology in the clinical practice of tuberculosis worked in the same way against dependence on X-ray findings causing long-term treatment. Also, the prefectures that had been less affected by the long-term treatment could depart faster from it.