Testing for Mycobacterium tuberculosis infection using the QuantiFERON-TB GOLD assay in patients with comorbid conditions in a tertiary care endemic setting

Abstract

Introduction: There were 10 million new cases of tuberculosis (TB) in 2017. To eliminate TB, it is necessary to diagnose active TB and latent tuberculosis infection (LTBI). Diagnosis of paucibacillary disease and in extrapulmonary TB (EPTB) remains challenging; low mycobacterial load can be missed by microbiological or molecular based confirmation; EPTB, can be misdiagnosed due to absence of site specific specimens for testing. Interferon gamma release assays (IGRA) use T cell-based Interferon-gamma (IFN-γ) to identify infection with M. tuberculosis (MTB) but cannot discriminate between active and LTBI. We investigated how IGRA was being used in a high burden low resource setting. Methods: We conducted a retrospective review of 149 consecutive cases received for QuantiFERON-TB Gold In-Tube Assay (QFT-GIT) testing in routine clinical service. Results: Fifty-six cases were QFT-GIT positive and 93 were QFT-GIT negative. Thirty-six per cent of QFT-GIT tested cases had active TB. Of QFT-GIT positive cases, 59% patients had active TB; 10 with pulmonary and 23 with extrapulmonary TB. The remaining 41% QFT-positive cases were LTBI. Of the QFT-GIT negative cases, 22% had active TB. Co-morbid conditions were present in 37% of QFT-GIT positive and 60% of QFT-GIT negative cases. Conclusions: Our study shows that IGRA is being used as an adjunct test for active TB in this population. It highlights the complexity of interpreting QFT-GIT results particularly for QFT-GIT negative cases when ruling out MTB infection.

Preliminary diagnostic performance of the VIDAS® TB-IGRA for the detection ofMycobacterium tuberculosisinfection and disease

“…The low sensitivity of the QFT-Plus in detecting TB disease cases has been well documented [13][14][15] , particularly in countries with a high prevalence of M. tuberculosis infection and other comorbidities 16,17 , such as Burkina Faso, which was one of our study sites. Additionally, there may be a potential correlation between the low sensitivity of the QFT-Plus and a high frequency of comorbidities, particularly parasitic infections and fecal yeast [18][19][20] , in these patients.…”