Frequency and Clinical Significance of a Variety of Autoantibodies in Patients With Definite Infective Endocarditis

Background: Patients with infective endocarditis (IE) may present rheumatic manifestations concurrent with autoantibodies with low specificity, thus increasing misdiagnosis. Frequency of autoantibodies with high specificity remains unknown. Methods: Nineteen patients with definite IE were studied for low specificity (rheumatoid factor [RF], antinuclear antibodies, anti-Ro/SSA, anti-La/SSB, anti-ribonucleoproteins (anti-RNP) anticardiolipin [aCL], and anti-beta(2) glycoprotein 1) and high specificity (anti-cyclic citrullinated peptides [anti-CCPs], anti-double-stranded DNA, anti-Sm, anti-Scl70, and anticentromere) antibodies. Results: Frequency of RF was 68%; antinuclear antibodies, 47%; aCL/IgG, 58%; aCL/IgM, 47%; anti-beta(2) glycoprotein 1/IgG, 5%; and anti-Ro/SSA, 5%. Three patients had antiphospholipid syndrome-related antibodies in high titers, one of them also having pulmonary embolism. Except for anti-CCP (1 patient), other highly specific antibodies were absent. Rheumatoid factor of 100 UI/mL or greater and multifocal endocarditis were independently associated with in-hospital mortality. Conclusions: Clinicians should need to be aware about the common presence of a variety of antibodies with low specificity but also the exceptional occurrence of anti-CCP antibodies in IE. Special attention to multifocal endocarditis and high RF is also suggested.