An Algorithm for Tuberculosis Screening and Diagnosis in People With HIV

Tuberculosis is a leading cause of death among adults with HIV. In some countries, up to 50 percent of these patients die during TB treatment, usually within two months of the TB diagnosis. Delayed diagnosis is probably a significant contributor to high mortality, an international team of researchers noted in this collaborative study.

While TB screening is recommended for those with HIV to facilitate antiretroviral and isoniazid preventive therapy, there are no internationally accepted, evidence-based guidelines for optimal screening. Nonetheless, screening for chronic cough is common.

In the current study, researchers consecutively enrolled 1,748 HIV patients from eight outpatient clinics in Cambodia, Thailand, and Vietnam, irrespective of evidence or absence of TB symptoms. Median CD4+ T-lymphocyte count was 242 per cubic millimeter; interquartile range 82-396. Three samples of sputum and one each of urine, stool, blood, and lymph-node aspirate (for those with lymphadenopathy) were obtained for mycobacterial culture. The team compared the characteristics of patients diagnosed with TB (on the basis of one or more culture-positive specimens) with TB-free patients to derive an algorithm for screening and diagnosis.

TB was diagnosed in 267 (15 percent) patients. Cough of two to three weeks duration in the preceding four weeks had a sensitivity of 22-33 percent for detecting TB. Cough of any duration, fever of any duration, or night sweats lasting three or more weeks in the preceding four weeks was 93 percent sensitive and 36 percent specific for TB. TB diagnosis was ruled out for the 1,199 patients with any symptoms with the help of a combination of two sputum-negative smears, normal chest radiograph, and CD4+ cell count of 350 or more per cubic millimeter. A positive diagnosis could be made for only 113 patients (9 percent) who had one or more positive sputum smears; mycobacterial culture was required for most other patients.

"In persons with HIV infection, screening for tuberculosis should include asking questions about a combination of symptoms rather than only about chronic cough," the authors concluded. "It is likely that antiretroviral therapy and isoniazid preventive therapy can be started safely in people whose screening for all three symptoms is negative, whereas diagnosis in most others will require mycobacterial culture."