[The decision making process in tuberculosis control programme]

The main purpose of this paper is to demonstrate relevance of the medical technology assessment (MTA) approach in the decision making process in the tuberculosis control programme. Recently MTA has progressed remarkably under the pressure of limited medical resources and necessity for rational utilization of those resources. This approach has also been assisted by the development in related technologies, such as statistics and the managerial sciences. The author demonstrates the feasibility of the MTA approach in tuberculosis control programmes, with special emphasis on the applicability of the mathematical model in risk-effectiveness analysis, citing several examples from his recent works. A critical analysis of the screening chest radiophotography (Mass Miniature Radiophotography, MMR) is a good sample of risk-effectiveness analysis, where benefit from early detection of tuberculosis is quantified and compared with the possible risk due to radiation exposure. A mathematical model is used to simulate the fate of tuberculosis patients with or without treatment. The benefit is computed in terms of lives saved, life-years extended, and treatment costs saved with or without the MMR programme. In Japan, it is concluded that MMR cannot be rationalized as a life-saving intervention in young age-groups, nor being economically cost-effective for wider age ranges. Based on the estimated trend of risk of infection of Japan now and in the near future, the infection status of a cohort born around 1990 can be calculated. Applying risk of clinical breakdown of tuberculosis to the above infection status and the assumed level of protective efficacy of BCG vaccination, assessment of the BCG vaccination programme can be made, under various hypothetical modes of vaccination, whether vaccinated to the newborn or to school entrants, whether revaccinated or not, and when, etc. The analysis revealed that the revaccination has very limited effectiveness, which in turn emphasizes the importance of the primary vaccination with optimum technical level. Under the very low prevalence conditions of tuberculous infection as in Japan of present (annual risk of infection estimated at ca. 0.05%), the determination of a cut-off point for selecting those eligible for chemoprophylaxis with isoniazid is a good example of a clinical decision problem which has a narrow spectrum of positive risk benefit ratio. Using the ROC analysis of the tuberculin testing, risk of excessive tuberculosis deaths and that of fatal hepatitis cases are compared under varying cut-offs, which leads to a conclusion that for the presumably very low-risk population chemoprophylaxis should be given to those with 20mm diameter or more of erythema.(ABSTRACT TRUNCATED AT 400 WORDS)