The leukocyte count in subacute bacterial endocarditis is usually normal, whereas a leukocytosis is commonly present in acute bacterial endocarditis. Normocytic normochromic anemia is often present in subacute bacterial endocarditis. The erythrocyte sedimentation rate is elevated in almost all patients with endocarditis except those with congestive heart failure.
Immunoglobulin abnormalities are frequent in infective endocarditis.
Circulating immune complexes have been demonstrated in more than 90 percent of patients with infective endocarditis. Hyperglobulinemia is common when the illness is prolonged. Occasionally, there have been reports of patients with IgG or IgM M components in their serum. Serum complement levels are low in some patients, particularly when endocarditis is complicated by immune complex glomerulonephritis. Renal abnormalities are common, and most patients have proteinuria and microscopic hematuria.