Diagnosis of NTM active infection in lymphadenopathy patients with anti-interferon-gamma auto-antibody using inhibitory ELISA vs. indirect ELISA

Arnone Nithichanon,Takayuki Matsumura,Yoshimasa Takahashi,Ploenchan Chetchotisakd,Manabu Ato,Takuro Sakagami,Ganjana Lertmemongkolchai

doi:10.1038/s41598-020-65933-x

Abstract

The anti-interferon-gamma (IFN-gamma) autoantibody is a known cause of opportunistic non-tuberculous mycobacterial (NTM) infection in adults. Diagnosis of those patients is difficult due to the low sensitivity of bacterial culture, and because detection of the neutralizing autoantibody needs special laboratory devices. We conducted a retrospective review of indirect and inhibitory ELISA, both used for detection of anti-IFN-gamma auto-antibody in 102 patients with lymphadenopathies. We assessed hospital records of NTM isolation and/or diagnosis of NTM infection. The review revealed the compatible sensitivity and superior specificity and predictive values for inhibitory ELISA over against indirect ELISA—the latter achieving 100% specificity and positive predictive value for diagnosis of NTM infection in patients with lymphadenopathies. The results confirm functional assays that show plasma samples from NTM-infected patients with positive results by either indirect and/or inhibitory ELISA are IFN-gamma neutralizing autoantibodies. The inhibitory titer of anti-IFN-gamma auto-antibody can be used to distinguish patients with active from inactive NTM infection. Inhibitory ELISA is thus a practical, rapid, high performance tool for routine detection of anti-IFN-gamma autoantibody and NTM infection diagnosis before confirmation, enabling a timely therapeutic strategy for active infection treatment.

Highlights

Non-tuberculous mycobacteria (NTM) are thought to be less pathogenic than Mycobacterium tuberculosis, which are commonly found in the environment worldwide[1]
A total of 102 lymphadenopathy patients with clinical manifestations of possible nontuberculous mycobacterial (NTM) infection were screened by a clinician and from whom heparinized whole blood was collected for routine detection of anti-human-IFN-γ autoantibody by inhibition titer and indirect Enzyme-linked immunosorbent assay (ELISA)
The cut-off for indirect ELISA was considered at 95% sensitivity and 90% specificity using a ROC curve (Supplementary Fig. S2)

Summary

Introduction

Non-tuberculous mycobacteria (NTM) are thought to be less pathogenic than Mycobacterium tuberculosis, which are commonly found in the environment worldwide[1]. NTM infection in non-HIV patients with anti-IFN-γ auto-antibodies has been reported in Taiwan and Thailand as highly associated with expression of the Asian human leukocyte antigen (HLA)[7,8,9,10], and more recently in Japanese NTM cases with anti-IFN-γ autoantibody[11]. Detection of the neutralizing anti-human-IFN-γ autoantibody is a crucial step in the diagnosis of NTM infection, thereby facilitating antibiotic management of affected patients[11]. Anti-human-IFN-γ auto-antibody can be detected based on different principals of ELISA (i.e., indirect ELISA11,17–19 or inhibitory ELISA7,14,20,21). We compared the diagnostic efficacy of anti-human-IFN-γ auto-antibody detection by indirect in comparison to inhibitory ELISA. We report on the anti-human-IFN-γ autoantibody titer as determined by ELISA for both the diagnosis and monitoring of infected patients

Methods

Results

Conclusion