Brief report: prevalence of antineutrophil cytoplasmic antibodies in infective endocarditis

Objective: Infective endocarditis (IE) mimics primary systemic vasculitis, and there are sporadic reports of positivity for antineutrophil cytoplasmic antibodies (ANCAs) among patients with IE. Because the frequency of ANCAs in IE is unknown, this study was undertaken to assess the seroprevalence of ANCAs in a large number of patients with IE.

Methods: The study was conducted in the framework of a single-center prospective cohort study of incident IE cases. Demographic, clinical, laboratory, and microbiologic data were collected, and magnetic resonance imaging of the brain was performed at diagnosis. For those patients whose serum had been stored at diagnosis, ANCAs were assessed by indirect immunofluorescence assay in ethanol-, formalin-, and methanol-fixed neutrophils. In addition, ANCA specificity for proteinase 3 (PR3) and myeloperoxidase (MPO) was assessed by enzyme-linked immunosorbent assay. Rheumatoid factor (RF), antinuclear antibodies (ANAs), anticardiolipin antibodies (aCL), and serum Ig levels were also measured. Comparisons between groups were made using Wilcoxon's rank sum and chi-square or Fisher's exact tests.

Results: Among 109 patients with IE, 18% had cytoplasmic ANCAs (cANCA) and/or perinuclear ANCAs (pANCA) and 8% had PR3-ANCAs or MPO-ANCAs, some with very high titers. Positivity for both cANCA or pANCA and PR3-ANCAs or MPO-ANCAs was found in 6% of patients, and RF, ANAs, and aCL were detected in 35%, 16%, and 23% of samples, respectively. No consistent clinical pattern of IE was observed in the anti-PR3/anti-MPO-positive IE patients, whereas positivity for cANCA/pANCA was associated with younger age (P = 0.022), more frequent occurrence of echocardiographic vegetations (P = 0.043), and above-normal serum IgG levels (P = 0.017).

Conclusion: ANCAs, including PR3- and MPO-ANCAs, occur in a substantial proportion of patients with IE. The link between cANCA/pANCA and specific features of IE requires further study.