Clinical Efficacy of Serum Antiglycopeptidolipid Core IgA Antibody Test for Screening Nontuberculous Mycobacterial Pulmonary Disease in Bronchiectasis

Background: The serum antiglycopeptidolipid core IgA antibody test has been proposed as a diagnostic tool for Mycobacterium avium complex pulmonary diseases. Cross-reactivity with other nontuberculous mycobacteria (NTM), including Mycobacterium abscessus, indicates that it may have a role as a broader screening test for nontuberculous mycobacterial pulmonary disease (NTM-PD). NTM-PD is believed to be underdiagnosed in patients with bronchiectasis. Research Question: Can the serum antiglycopeptidolipid core IgA antibody test be used to screen for NTM-PD in bronchiectasis? Study Design and Methods: Patients from the prospective European Bronchiectasis Registry (European Multicentre Bronchiectasis Audit and Research Collaboration-Bronchiectasis Research Involving Databases, Genomics and Endotyping; ClinicalTrails.gov Identifier: NCT03791086) were enrolled. Patients from the United Kingdom, Italy, Spain, Belgium, The Netherlands, and Germany were included. A control cohort of patients without any underlying lung disease also was recruited. The levels of serum IgA antibodies against the glycopeptidolipid core were measured using an enzyme immunoassay kit, and receiver operating characteristics curve analysis was conducted to evaluate the accuracy of the antibody level in screening for NTM-PD. Results: Two hundred eighty-two patients were enrolled (151 female patients [53.6%]; median age, 68 years). Median antiglycopeptidolipid core IgA antibody levels were 0.2 U/mL (interquartile range [IQR], 0.1-0.3 U/mL) in patients without NTM isolation and NTM-PD (n = 238), 0.3 U/mL (IQR, 0.2-0.4 U/mL) in patients with NTM isolation that was incompatible with the diagnosis of NTM-PD (n = 18), and 1.5 U/mL (IQR, 0.4-6.2 U/mL) in patients with NTM-PD (n = 26; P = .0001). Antibody levels showed excellent accuracy in identifying patients with NTM-PD (area under the receiver operating characteristic curve, 0.886; 95% CI, 0.800-0.973) in the bronchiectasis cohort and also showed excellent discrimination of patients with NTM-PD from those with NTM isolation who did not meet the diagnostic criteria for NTM-PD (0.816; 95% CI, 0.687-0.945). Interpretation: The antiglycopeptidolipid core IgA antibody demonstrated excellent efficacy in screening for NTM-PD in a large cohort of patients with bronchiectasis. Clinical Trial Registry: ClinicalTrials.gov; No.: NCT03791086; URL: www.clinicaltrials.gov