[Preventable tuberculosis cases in Japan--a new approach to the assessment of tuberculosis control problems].

I defined cases of tuberculosis which could not be prevented from infection or development of disease among infected, or could not be detected in the early stages as "preventable cases" in order to evaluate tuberculosis control efforts in the community, Japan. Among 241 bacteriologically confirmed cases with pulmonary tuberculosis newly registered from 1988 through 1989 in Yamagata Prefecture, 80 (33%) were defined as preventable cases by observing their course and the process of diagnosis. That is to say, one-third of bacillary cases could have been prevented in Yamagata where the incidence of tuberculosis was lowest in Japan, if existing prevention and control methods had been effectively used. Causes of prevention failure were investigated in detail. The most common cause was tardy detection of cases, especially due to delayed confirmation of diagnosis (so called "doctor's delay"). The delayed confirmation of diagnosis resulted from neglecting chest X-ray and sputum examination and from ignoring high risk groups. In the younger age group, it was mainly attributed to insufficient family contact examinations. Tuberculin skin tests are necessary not only for those aged 15 years and younger but also for those aged 16-29, when they are found to be household contacts of smear-positive cases. An evaluation of tuberculosis control program defining preventable cases would be a beneficial approach to the surveillance of tuberculosis.