Many of the tests that are most commonly used to diagnose tuberculosis (TB) may be inaccurate for diagnosing approximately 50 percent of pregnant women who have HIV infections.
This research, published in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine online, included two tests: the Quantiferon Gold in Tube (QGIT) blood test and the TB skin test (TST). The researchers compared the effectiveness of the two tests in this specific population.
Because pregnancy and HIV infections both weaken the immune system, there are significantly more risks that these women will develop active TB.
"The World Health Organization and many governments endorse the TST because it is a cheap and ubiquitous test," Dr. Jyoti Mathad, lead study author and instructor of medicine in the Center for Global Health at Weill Cornell Medical College, said. "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. We found that QGIT positivity was almost three times higher than the more widely used TST at every time point tested.”
The researchers found 252 women volunteers who were all in their second or third trimester and were accepting care in India’s public teaching hospital. The women gave blood samples and took TB tests at enrollment and also at delivery and three months postpartum.
"Our blood data suggests that pregnant women produce lower levels of the immune chemicals that many TB diagnostics look for,” Mathad said. “This finding has implications beyond diagnostics. 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."