TB Testing

Proper diagnosis of LTBI versus active TB is crucial, because LTBI can rapidly progress to TB disease, particularly in PLWHA. LTBI can be diagnosed by tuberculin skin test (TST; also called PPD [purified protein derivative], the protein used in the skin test) or, less commonly, by using interferon-gamma release assay (IGRA) blood tests. TST results need to be read by a health care provider 2 to 3 days after the test is placed. (See insert, Table 1, for more on LTBI testing.)

Since 1989, the CDC has recommended HIV testing for all TB patients, and TB testing has been recommended for all PLWHA for more than a decade.10 Shockingly, a recent study reported that only 54 percent of newly diagnosed HIV patients in the United States received a TST.11 And in 2005, only 69 percent (7,689 of 11,193) of TB patients had ever been tested for HIV; among TB patients with known HIV status, 13 percent (1,034) were HIV positive.12

The 2008 U.S. Guidelines for Prevention and Treatment of Opportunistic Infections recommend LTBI testing upon HIV diagnosis and retesting for people whose CD4 nadir reaches <200 cells/µL (but testing should take place after patients begin antiretroviral therapy [ART] and their CD4 cell count increases to ≥200 cells/µL). Annual testing is recommended for PLWHA at risk for TB (e.g., people who have been in close contact with infectious TB patients, have been incarcerated, or live in homeless shelters or other congregate settings; injection and noninjection drug users; children; and people with other sociodemographic risk factors for TB; see insert, Figure 1).13,14

HRSA’s HIV/AIDS Bureau’s Core Clinical Performance Measures for Adults and Adolescents sets forth performance measurement recommendations for TB testing for PLWHA. The goal of performance measures is to improve the quality of care—including TB screening. Because the issue of TB reflects an important aspect of care that affects HIV-related morbidity and mortality and highlights treatment decisions that affect a sizeable population, Ryan White HIV/AIDS Program grantees are encouraged to track the number of clients who have received documented testing for LTBI since HIV diagnosis. Grantees are also encouraged to track the number of PLWHA who do not have a history of positive TB tests or a previous documented positive TST or IGRA. In doing so, grantees will be able to improve quality management and early TB detection and will be able to monitor their findings for areas of improvement.

Increasing testing among PLWHA is critical, because TB diagnosis can be complicated in people who are HIV positive. Chest x-rays may be normal or atypical, and unusual manifestations of TB, including disseminated and extrapulmonary TB (i.e., infection of the kidney, lymph nodes, pleura, spine, brain, and genitourinary tract, among other parts of the body), are far more common among PLWHA—particularly women—than among people who are HIV negative.15,16,17,18 In addition, immunosuppression increases the risk for extrapulmonary TB, although it can occur at any CD4 cell count. PLWHA with extrapulmonary TB are at high risk for disseminated TB, which can progress rapidly and can cause high fevers and sepsis syndrome.

Testing, diagnosis, and treatment recommendations do not differ for HIV-positive pregnant women. TB that goes untreated until late pregnancy can cause complications, such as premature birth, low birthweight and, rarely, congenital TB.

*Marks, SM. Division of Tuberculosis Elimination and Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention. Personal communication. December 29, 2008.