Evaluation of a tuberculosis mass survey conducted in the city of Chatham and in Kent County, Ontario, in 1963.

Computer analysis of the results of a mass tuberculosis survey of the population of Chatham city and Kent County, Ontario, was carried out to assess the efficacy of such surveys as a case-finding device. Six cases of active tuberculosis were found during the survey and approximately 50% of the 89,427 inhabitants of Chatham and Kent County were surveyed with radiographs and Heaf skin tests.A follow-up study of the Heaf test conducted in the public school of Wallaceburg detected 70 Heaf-positive children out of a total of 1190. These Heaf-positive children were further tested with a Mantoux test (5 T.U.) and chest radiography. Only 11 children of the original 70 were Mantoux-positive.These findings further support the hypothesis that the Heaf test, as now read, over-reads for M. tuberculosis infections.