The Pediatric infectious disease journal 2017 11 14() doi 10.1097/INF.0000000000001792
The T-SPOT.TB, an interferon-γ release assay (IGRA), is an indirect test of Mycobacterium tuberculosis infection. Due to sparse and conflicting evidence, IGRA use is limited in young and HIV-infected children. We determined the prevalence of invalid, borderline, positive, and negative results and associations with key demographic variables during routine pediatric use in a TB low-burden setting.
For pediatric samples received at Oxford Diagnostic Laboratories from 2010-2015, the associations between initial test outcome and demographics were estimated by bivariate analysis and logistic regression.
44,289 samples (median age 12.5 years; IQR 7.7-15.5), including 5,057 samples (11.6 %) from children under five years old, were received from 46 U.S. states, Washington, DC and Puerto Rico. 592 samples (1.3%) could not be tested. T-SPOT.TB positivity was strongly correlated (r=0.60; p<0.0001) with state TB incidence. Compared to negative results, positive results were more likely in samples from older children (p<0.0001), public health clinics (p<0.0001), and rural locations (p=0.005). Although infrequent (0.6%), invalid results were more common in samples collected at HIV clinics (OR=2.5, 95% CI 1.3-4.9) and from younger children (p=0.03). These invalid results were more likely due to a robust nil (negative) control response rather than a weak mitogen (positive) control response. CONCLUSIONS
The T-SPOT.TB test correlated strongly with well-recognized risk factors for tuberculosis infection and provided evaluable results in 98% of children. To optimize the impact f testing on clinical decision making and patient outcomes, local epidemiology and individual patient risk should be considered when incorporating IGRAs into pediatric guidelines.