Silicotuberculosis: long-term outcome after short-course chemotherapy.

SETTING

A medical facility for approximately 90,000 gold miners employed on 24 South African gold mines.

OBJECTIVE

To establish the long-term risk attributable to silicosis of relapse from pulmonary tuberculosis treated with short-course chemotherapy.

DESIGN

A consecutive sample of gold miners with pulmonary tuberculosis allocated to receive rifampicin, isoniazid, pyrazinamide and streptomycin given on weekdays for 5 months. Radiographs were assessed at the time of diagnosis for the presence of silicosis. All of the men were followed for at least 5 years after completing their treatment, or until they left mine service or suffered a relapse of tuberculosis.

RESULTS

The sample included 549 men of whom 167 had silicosis. The incidence density for relapse in silicosis was 1.55 (95% CI 0.97, 2.48) times that for the men without silicosis. There was no difference in the pattern of relapse over time between the two groups: the mean period to relapse in the men with silicosis was 2.6 years (SD 1.89 years) and for the men without silicosis was 3.1 years (SD 2.23 years) (P = 0.6).

CONCLUSION

Silicosis causes a small increase in the risk of relapse of tuberculosis. Relapses in both groups were not confined to the first 2 years after completion of treatment.