Interferon Gamma Release Assays in Patients with Respiratory Isolates of Non-Tuberculous Mycobacteria – a Preliminary Study

Abstract

Interferon gamma releasing assays (IGRAs) are extensively used in the diagnosis of latent tuberculosis infections. Comparing to tuberculin skin test (TST) they lack false positive results in the populations vaccinated with BCG, and in most non-tuberculous mycobacteria (NTM) infections. Nevertheless, Mycobacterium kansasii, Mycobacterium marinum, and Mycobacterium szulgai may induce positive IGRAs due to RD1 homology with Mycobacterium tuberculosis. The aim of the study was to investigate the possible influence of NTM respiratory isolates on the results of IGRAs. 39 patients (23 females and 16 males) of median age 61 years, with negative medical history concerning tuberculosis, entered the study. Identification of NTM was performed using the niacin test and molecular method GenoType CM test (Hain Lifescience). QFT-Plus was performed in 17 patients, T-SPOT-Tb – in 23 patients. Chest X-rays and a high-resolution computed tomography of the chest have been reviewed by the experienced radiologist blinded to the results of IGRAs, in search of past tuberculosis signs. Positive IGRAs results were obtained in three out of 39 patients (8%): 22% of patients with M. kansasii isolates and 18% of patients with radiological signs on HRCT that might be suggestive of past tuberculosis. Positive IGRAs correlated with radiological signs suggestive of past tuberculosis (r = 0.32, p = 0.04), and on the borderline with isolation of M. kansasii (r = 0.29, p = 0.06). These findings may suggest that a positive IGRAs result, in our material, could depend mostly on asymptomatic past Tb infection. The cross-reactivity of M. kansasii isolates with IGRAs was less probable; nevertheless, it requires further investigations.

Establishment and validation of a predictive model for nontuberculous mycobacterial infections in acid‐fast bacilli smear‐positive patients

“…So, most of NTM infection could have negative results. In our study, a negative test for QFT is more common in NTM patients, it was also found in other studies, 16,17 and through our multivariate regression analysis, it was found an independent risk factor for predicting NTM, which might be an important factor for differential diagnosis.…”

“…Meanwhile, 17.2% of NTM patients presented positive QFT results in our investigation. As we know, IGRAs are specific for M. tuberculosis and not encoded in the genomes of any Bacillus Calmette–Guerin (BCG) vaccine strains or most species of NTM, other than M. marinum , M. kansasii , M. szulgai and M. flavescens 16 . However, not all NTMs have been studied for cross‐reactivity.…”

Performance of Interferon-Gamma Release Assays in the Diagnosis of Nontuberculous Mycobacterial Diseases—A Retrospective Survey From 2011 to 2019

“…Meanwhile, some NTM species ( M. kansasii , M. marinum and M. szulgai ) sharing RD1 with M. tuberculosis showed similar positive results with IGRAs as M. tuberculosis ( Hermansen et al., 2014 ; Chen et al., 2018 ; Augustynowicz-Kopeć et al., 2019 ), and the feasibility of differentiating these species from PTB was doubtful. Our analysis suggested there was no statistically significant difference of IGRAs performances between any species of NTM.…”

“…Hermansen reported the QFT-G positivity rate was 8% (4/53) in definite NTM disease and 31% (15/49) in possible disease with colonization, while the overall rate of positive QFT-G in pulmonary NTM disease defined patients was 18% (81/462) by their systematic review ( Hermansen et al., 2014 ). Augustynowicz-Kopeć reported that the positive IGRAs result was 8% in NTM definite patients (3/39) ( Augustynowicz-Kopeć et al., 2019 ). Wang stated that the positivity rate of T-SPOT.TB was 53.4% (31/58) among the probable and definite NTM groups, 53.5% (15/28) for probable cases and 53.3% (16/30) for definite cases ( Wang et al., 2016 ).…”

Mycobacterium chimaera as an Underestimated Cause of NTM Lung Diseases in Patients Hospitalized in Pulmonary Wards

“…A similar observation was made by Moon et al (2016) , who found past lung tuberculosis in 64% of patients with M. chimaera infection. The other NTM type often responsible for NTMLD in patients with post-tuberculous lung lesions is Mycobacterium kansasii ( Augustynowicz-Kopeć et al 2019 ). It is not known whether the higher incidence of NTMLD in those NTM-infected patients, who had a history of past tuberculosis, is related to the favorable conditions for their colonization in the altered lung parenchyma, or a defect in the intracellular killing of NTM in these patients.…”