Tuberculin sensitivity testing and treatment of latent tuberculosis remains effective for tuberculosis control in human immunodeficiency virus-infected patients in Hong Kong.

OBJECTIVE

To evaluate whether a policy to treat latent tuberculosis identified by annual tuberculin sensitivity testing is effective for tuberculosis control in human immunodeficiency virus-infected patients in Hong Kong.

DESIGN

Historical cohort study.

SETTING

Integrated Treatment Centre, Department of Health, Hong Kong.

PATIENTS

Patients infected with human immunodeficiency virus without a history of tuberculosis were offered annual tuberculin sensitivity testing, coupled with treatment of latent tuberculosis if they tested positive. All such patients were followed for new tuberculosis.

RESULTS

In all, 1154 patients on antiretroviral therapy, contributing to 5587 patient-years of observation, were analysed; 1032 patients (89%) received annual tuberculin sensitivity testing. Their baseline characteristics, including CD4 counts and other risk factors for tuberculosis, did not differ significantly from those who declined testing. The overall incidence rate of tuberculosis was 0.59 case per 100 patient-years. It was lower in those who received annual tuberculin sensitivity testing than those who did not (0.41 vs 3.85 per 100 patient-years; P<0.0001). Only a low baseline CD4 count and a history of tuberculin sensitivity testing were shown to be significant indicators of incident tuberculosis using multivariate analysis. The hazard ratio was 0.36 (95% confidence interval, 0.16-0.85; P=0.02) for those with a baseline CD4 count of 100/mm3 or above, and 0.26 (95% confidence interval, 0.08-0.77; P=0.016) for those who received annual tuberculin sensitivity testing. The incidence of tuberculosis was highest within 90 days of antiretroviral therapy initiation.

CONCLUSION

The established policy continues to be effective. The high risk of tuberculosis during the early period of antiretroviral therapy supports early use of tuberculin sensitivity testing. Alternatively, the strategy of universal isoniazid preventive therapy at antiretroviral therapy initiation could be studied for those with very low baseline CD4 counts.