Microbiological patterns of ANCA-positive infective endocarditis: a laboratory perspective

Anti-neutrophil cytoplasmic antibody (ANCA)-positive infective endocarditis (IE) frequently mimics primary ANCA-associated vasculitis, particularly in subacute presentations with renal involvement, and may lead to diagnostic delay or inappropriate immunosuppression. From a laboratory perspective, we reviewed published individual case reports of ANCA-positive IE with explicit microbiological identification and reported outcomes. Fifty-two cases were analyzed using a structured dataset focusing on pathogen distribution, blood-culture status, ANCA assay patterns, renal manifestations, and immune-complex–associated serologies. Bartonella species were the most common pathogens (16/52, 30.8 %) and were uniformly associated with culture-negative IE (16/16, 100 %), contributing substantially to the overall frequency of culture-negative cases (21/52, 40.4 %). PR3-ANCA–predominant results accounted for 78.8 % of cases, whereas MPO-ANCA predominance was rare (1.9 %). Renal involvement was frequent: acute kidney injury occurred in 73.1 % of patients, and rapidly progressive or crescentic glomerulonephritis in 55.7 %. Immune-complex–related findings were common, including hypocomplementemia (59.6 %), rheumatoid factor positivity (44.2 %), and cryoglobulinemia (26.9 %); renal pathology was heterogeneous, with both immune-complex and pauci-immune patterns reported. These case-level data highlight a distinct laboratory signature of ANCA-positive IE characterized by Bartonella -driven culture-negative infection, PR3-ANCA predominance, and severe renal involvement – features that promote diagnostic anchoring toward vasculitis. Integrated laboratory diagnostics, including early laboratory–clinician communication, context-aware interpretation of ANCA results, optimized blood-culture strategies, and targeted testing for fastidious organisms (notably Bartonella ), in conjunction with echocardiographic evaluation, are essential to improve diagnostic accuracy and avoid inappropriate immunosuppression.