Comparison of two interferon gamma release assays in the diagnosis of Mycobacterium tuberculosis infection and disease in The Gambia

Abstract

Background: IFN-γ Release Assays (IGRAs) have been licensed for the diagnosis of latent Mycobacterium tuberculosis infection (LTBI). Their performance may depend on assay format and may vary across populations and settings. We compared the diagnostic performance of an in-house T -cell and commercial whole blood-based IGRAs for the diagnosis of LTBI and TB disease in The Gambia.

Comparison of performance in two diagnostic methods for tuberculosis infection

“…However, although the early reported speciWcities of T-SPOT were 100% [17][18][19][20], the speciWcity of T-SPOT in this study appears to be statistically low compared with that of QFT-G. In studies in which performance of both tests were directly compared, many of them did not compare the speciWcity using healthy controls [10,[12][13][14][15]. Among them, Lee et al [11] have reported that the speciWcity of T-SPOT was lower than that of QFT-G using healthy controls, though the diVerence was not statistically signiWcant.…”

“…Another system, T-SPOT ® .TB (T-SPOT), utilizes puriWed PBMC from whole blood as specimens and enzyme-linked immunospot (ELISPOT) assay for detection of produced IFN-. Although both tests have been shown to have higher sensitivity and speciWcity to diagnose active TB as well as LTBI compared with TST in numerous studies [9], the number of studies in which performance of both tests were directly compared are rather limited [10][11][12][13][14][15]. As the performance of each test may vary depending on settings, it is important to compare the performance of both tests in the same setting, especially the speciWcity in countries with intermediate prevalence of TB.…”

Discordance among Commercially Available Diagnostics for Latent Tuberculosis Infection

“…Several studies have compared results from different IGRAs and from TST "head-to-head" (28,(36)(37)(38)(39)(40)(41)(42), and although the agreement between QFT-GIT and T-Spot has generally been very good, discordant results between the IGRA and TST have been found in up to 20-30% of subjects (3). The magnitude of discordance is demonstrated in this study by the low kappa values and the high proportion of discordance seen among positives, because 68 (77%) of 88 individuals with at least one positive test were positive to only one of the three tests.…”

Tuberculosis contact investigation in low prevalence countries: a European consensus

“…Nevertheless, given the high predictive value of a negative test result in a healthy population with a low expected prevalence, the use of a negative IGRA may be justifiable to support exclusion of tuberculosis [117,118]. A negative response in an IGRA should nevertheless not dissuade a clinician to diagnose and treat presumptive tuberculosis, especially in immunosuppressed individuals and children [119,120].…”