Comparing an Interferon Gamma Release Assay with the Tuberculin Skin Test During Pregnancy: Implications for...

Background Currently there are no guidelines regarding optimal screening for latent tuberculosis infection during pregnancy. Objective This study measures completion rates and the concordance between the TSPOT.TB, a commercially available interferon gamma release assay (IGRA), and the traditional tuberculin skin test (TST) in a predominantly urban minority obstetrics practice. Design This is an observational cohort study of 141 pregnant women enrolled from an obstetrics practice with a large immigrant population. Women with a history of a positive TST result were excluded. Demographic and clinical risk factors for tuberculosis were assessed. Enrolled women underwent a T-SPOT.TB test and placement of TST, and returned in 48-72 h for TST interpretation. We calculated the completion rate and frequency of a positive result for each test, as well as the concordance between the T-SPOT.TB and TST. Results Among the 141 women enrolled, 75 % were either Latina or African-American, 44 % were born in a country with a high TB prevalence, and 52 % had received the Bacillus Calmette-Guerin vaccine. Seven women (5 %) had a positive screening test, a total of 3 positive T-SPOT.TB results and 6 positive TST results, and all were from countries with a high TB prevalence. The concordance of the two tests was 96.3 %. The completion rate for the T-SPOT.TB was 98 %, while the completion rate for the TST was 63 %.

The IGRA test had a markedly higher completion rate in addition to maintaining high concordance with the two-step TST in this population of pregnant women with a high prevalence of prior TB exposure. Targeted screening of women from countries with a high prevalence of tuberculosis may be warranted during prenatal care.