Gaps in MPO and PR3 ELISA Performance in ANCA-Associated Vasculitis: A Thai Cohort Analysis

บทคัดย่อ

Objective: Early and accurate diagnosis of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is critical to initiating appropriate treatment and for improving patient outcomes. Delayed diagnosis may result in irreversible organ damage, prolonged disease activity and increased mortality. Although, myeloperoxidase (MPO)-ANCA and proteinase 3 (PR3)-ANCA detection by enzyme-linked immunosorbent assay (ELISA) is widely implemented, diagnostic performance may vary across different AAV subtypes and ethnic populations. This study aimed to assess the diagnostic accuracy of MPO-ANCA and PR3-ANCA ELISA in a hospital-based cohort of Thai patients.
Material and Methods: A retrospective analysis was conducted on clinical and serological data from a hospital-based Thai cohort of patients tested for ANCA, using MPO and PR3 ELISA; from January 2019 until August 2024. Sensitivity and specificity were calculated using confirmed AAV diagnoses as the reference standard.
Results: Among the 55 confirmed AAV cases, ELISA detected MPO-ANCA or PR3-ANCA in 39 cases (70.9% sensitivity), and showed 95.0% specificity among non-AAV controls. Subtype analysis revealed the highest sensitivity for microscopic polyangiitis (MPA, 76.7%) and granulomatosis with polyangiitis (GPA, 66.7%), but low sensitivity for eosinophilic granulomatosis with polyangiitis (EGPA, <30.0%). MPA was the most common subtype (48.4%), with a median age of 67 years. ELISA failed to detect ANCA in 29.1% of the confirmed AAV cases, most of which were EGPA.
Conclusion: MPO-ANCA and PR3-ANCA ELISA are highly specific; however, they have limited sensitivity, particularly for EGPA. Given the regional variations in AAV subtype prevalence, reliance on ELISA alone may cause underdiagnosis. Complementary testing strategies may improve detection of ELISA-negative samples.