Tuberc Respir Dis.  1977 Jun;24(2):39-48. 10.4046/trd.1977.24.2.39.

Report on the Third National Tuberculosis Prevalence Survey

• KMID: 2528942
• DOI: http://doi.org/10.4046/trd.1977.24.2.39

Abstract

The third national tuberculosis prevalence survey was conducted in the systematically selected sample areas from 20 March to 15 September 1975. The survey consisted of tuberculin testing, and X-ray and bacteriological examinations. All the methods and procedures applied were identical as those of the two previous surveys. The sample size was increased to 31018 in the 1975 survey in order to obtain narrower confidence limits. The following is the main findings of the 1975 survey. (1) The coverage of BCG vaccination increased remarkably particularly among the pre-school and school-age children in the intervals between the three surveys. (2) The prevalence of infection shown by the proportion of tuberculin positive reactors among persons without BCG scar decreased remarkably particularly among the younger age groups of 0-4, 5-9 and 10-14 years. (3) The prevalence of radiologically significant pulmonary tuberculosis decreased to 3.3% in 1975 as compared with 4. 2% in 1970 and 5.1% in 1965. The 95% confidence limits of the 1975 rate did not overlap with those of the 1970 and 1965 rates. The decrease in the prevalence of radiologically significant pulmonary tuberculosis was statistically significant (4) The prevalence of bacteriologically confirmed pulmonary tuberculosis in the three surveys was 0.94% in 1965, 0.74% in 1970 and 0.76% in 1975. The 95% confidence limits of these three rates overlapped. (5) The proportion of microscopy negative and culture positive cases among the total confirmed cases increased between the previous two surveys and the 1975 survey, and the increase from 1970 to 1975 was statistically significant. Microscopy negative and culture positive cases are known to be less infectious than microscopy positive cases. This might partially explain the discrepancy between no change in prevaleilce of bacteriologically confirmed pulmonary tuberculosis and the marked decrease in prevalence of tuberculin positive reactors among younger children. (6) The overall prevalence of tubercle bacilli showing resistance to one or more of the standard antituberculous drugs (lNH, PAS and SM) was 38.2% in 1975, and there was no change compared to previous two surveys. However the prevalence of resistance to any one drug decreased while the prevalence of resistance to two drugs increased. (7) AIl persons eligible for X- ray examination were .interrogated for symptoms. The prevalence of respiratory symptom decreased greatly in 1975 as compared with two previous surveys. Among the seven symptoms for which patients were interrogated, haemoptysis indicated the highest tisk of tuberculosis