TST often misses TB in pregnant HIV+ women
New research finds that the most commonly used test for tuberculosis fails to accurately diagnose TB in up to 50 percent of pregnant women who are HIV positive.
“The World Health Organization and many governments endorse the TST [tuberculin skin test] because it is a cheap and ubiquitous test,” lead study author Jyoti Mathad, MD, said in a statement. “However, our over-reliance on this single test means that we are failing to detect and treat a potentially life-threatening infection in tens of millions of high-risk women.” Dr. Mathad is instructor of medicine in the Center for Global Health at Weill Cornell Medical College in New York.
“We found that QGIT positivity was almost three times higher than the more widely used TST at every time point tested,” noted the authors (Mathad JS, et al. Am J Respir Crit Care Med. Published online ahead of print Jan. 14, 2016. doi:10.1164/rccm.201508-1595OC).
Dr. Mathad and her colleagues enrolled 252 women who were in their second or third trimester and receiving care at a public teaching hospital in India. The women received TB testing at enrollment during pregnancy or at delivery. An additional 39 women participated in a longitudinal study to assess how the TB tests were affected by changes in different stages of pregnancy. They were tested at delivery and three months postpartum. The researchers also collected blood samples to assess for levels of infection-fighting proteins.
“Our blood data suggests that pregnant women produce lower levels of the immune chemicals that many TB diagnostics look for. This finding has implications beyond diagnostics,” Dr. Mathad said. “For example, not all pregnant women lose immune control of TB infection. But, currently, we have no way of predicting which women are most likely to get sick from the disease. Our findings about these immune chemicals provide a starting point for developing a test that will tell us who in this already high-risk population is at greatest risk of disease and death and is in most need of treatment.” She added that this insight about indicators of risk would also benefit other high-risk groups such as the elderly, young children, and all people who are HIV positive.