[Mass health examination for tuberculosis].

Miniature radiography or radiophotography (RP) was first developed independently by de Abreu M of Brazil and Koga Y of Japan in 1936, and because of its utility, it was used as a tool of mass health examination for TB all over the world soon after its development. The idea of RP is to take a picture of the chest X-ray image on a fluorescent screen set in a dark box, and this idea was materialized through development of a camera with a small F-number. Through application of RP as a tool for mass health examination, many TB cases had been detected, and most of these had been previously unknown cases. In the TB Control Law legislated in 1951, the three major components were (1) early detection of TB cases by mass miniature radiography (MMR), (2) prevention of TB by BCG vaccination, and (3) distribution of adequate TB treatment. MMR first covered the population below 30 years of age, as it was thought that the prevalence of TB was high among young adults. However, based on the results of the TB Prevalence Survey in 1953, it was expanded to the whole population in 1955, and since 1957, all MMR, tuberculin skin tests, and BCG vaccinations have been carried out free of charge for community residents in Japan. The expenses are shared, in equal thirds, by the central government, the prefectural government, and the community office. The numbers of persons examined by MMR are shown in Fig. 1, and the detection rate of TB cases by MMR and other health examinations are shown in Fig. 2. In accordance with the decline in TB, the number of MMR subjects has gradually been reduced, starting with primary and junior high school students and then with senior high school students, to a point where cases are now confined to those 65 years of age and above and inhabitants living in TB high-incidence areas. The most marked outcomes had been obtained in big enterprises, in which twice yearly MMR had been carried out. These efforts had resulted in a significant rapid decline in cases of TB requiring absence from work as shown in Fig. 3. As sick leave and cost for medical care were secured for 3 years for TB cases in big enterprises in Japan, this rapid decline contributed to the rise of productivity of big enterprises and ultimately to rapid growth of the GNP of Japan. In big enterprises in Japan, in contrast to the rapid decline of TB, the incidence of cancer and other lifestyle-related diseases had increased, and annual examinations for new diseases were introduced as a control measure without thorough analysis of the effectiveness of these examinations. In the case of MMR for TB, before its use as a control measure, procedures including detailed examinations and post-examination management were fully tested, and outcomes were evaluated, and such procedures were needed for health examinations for cancer and other lifestyle-related diseases. The contribution of MMR to the rapid decline of TB in Japan has been highly evaluated, however, success of MMR has resulted in the decline of detection rate of TB, thus deteriorate the cost-effectiveness of MMR. Timing of reducing its use has not been sufficiently examined, and it might be done a little bit earlier.