Diagnostic accuracy of tuberculin skin test self-reading by HIV patients in a low-resource setting.

BACKGROUND

The World Health Organization recommends tuberculin skin tests (TSTs) where feasible to identify individuals most likely to benefit from isoniazid preventive therapy (IPT). The requirement for TST reading after 48-72 h by a trained nurse is a barrier to implementation and increases loss to follow-up.

METHODS

Patients with human immunodeficiency virus (HIV) infection were recruited from a primary care clinic in South Africa and trained by a lay counsellor to interpret their own TST. The TST was placed by a nurse, and the patient was asked to return 2 days later with their self-reading result, followed by blinded reading by a trained nurse (reference).

RESULTS

Of 227 patients, 210 returned for TST reading; 78% interpreted their test correctly: those interpreting it as negative were more likely to be correct (negative predictive value 93%) than those interpreting it as positive (positive predictive value 42%); 10/36 (28%) positive TST results were read as negative by the patient.

CONCLUSIONS

Patients with HIV in low-resource settings can be trained to interpret their own TST. Those interpreting it as positive should return to the clinic within 48-72 h for confirmatory reading and IPT initiation; those with a negative interpretation can return at their next scheduled visit and initiate IPT at that time if appropriate.