Tuberculosis risk factors in a silicotic cohort in Hong Kong.

SETTING

Hong Kong silicotic patients are followed regularly at the Pneumoconiosis Clinic.

OBJECTIVE

To quantify the incidence of tuberculosis disease that occurs after the date of diagnosis of silicosis (DOD), and to identify the risk factors for its development.

DESIGN

Retrospective analysis of a Hong Kong silicotic cohort with DOD from 1 January 1988 to 31 December 1993.

RESULTS

Of 718 subjects whose records were identified, 11 were excluded from the study. The incidence of tuberculosis (TB) after DOD was 3019 patients per 100,000 population, approximately nine times that of the local population matched for age and sex. Twelve factors were subject to univariate analysis 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 [CI] 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). Relative risks were calculated for patient subgroups stratified according to TB risk factors.

CONCLUSION

This study has reaffirmed the strong association of tuberculosis and silicosis, and has identified several TB risk factors with a logistic regression model.