Tuberculosis risk factors in a silicotic cohort in Hong Kong

SETTING: Hong Kong silicotic patients are followed regularly at the Pneumoc oniosis Clinic. OBJECTIVE: To quantify the incidence of tuberculosis disease that occurs af ter the date of diagnosis of silicosis (DOD), and to identify the risk fact ors for its development. DESIGN: Retrospective analysis of a Hong Kong silicotic cohort with DOD fro m 1 January 1988 to 31 December 1993. RESULTS: Of 718 subjects whose records were identified, 11 were excluded fr om the study. The incidence of tuberculosis (TB) after DOD was 3019 patient s per 100000 population, approximately nine times that of the local populat ion matched for age and sex. Twelve factors were subject to univariate anal ysis followed by logistic regression. Four TB risk factors were identified: 1) no anti-tuberculosis treatment before DOD (relative risk [RR] 4.51, 95% confidence interval [Cr] 2.46-8.24), 2) progressive massive fibrosis (PMF) (RR 3.78, 95% CI 2.25-6.36), 3) small opacities exceeding 1.5 mm (RR 2.17, 95 % CI 1.38-3.42), and 4) caisson work (RR 1.56, 95% CI 1.01-2.41). Relat ive risks were calculated for patient subgroups stratified according to TB risk factors. CONCLUSION: This study has reaffirmed the strong association of tuberculosi s and silicosis, and has identified several TB risk factors with a logistic regression model.