Prognostic value of serial C-reactive protein measurements in left-sided native valve endocarditis

The clinical course of left-sided native valve infective endocarditis varies from uncomplicated disease to fulminant infection. Although several factors are known to affect clinical outcome, it is difficult to predict morbidity and mortality in individual patients. The objective of this study was to determine the value of serial C-reactive protein (CRP) measurements as a predictor of clinical outcome.

One hundred twenty-three consecutive patients who fulfilled the Duke criteria for definite left-sided native valve infective endocarditis were prospectively enrolled. Poor outcome was defined as serious infectious complications or death. Patients were followed up for 12 weeks after the end of antimicrobial therapy. Multivariate analysis was used to examine the relative importance of the CRP level as a predictor of poor outcome after adjusting for age, abscess, multivalvular involvement, and Staphylococcus aureus infection.

After 1 week of therapy, the adjusted odds ratio for poor outcome was 10.3 (95% confidence interval, 2.2-49.4) for patients with CRP levels in the highest tertile (>122 mg/L [to convert to nanomoles per liter, multiply by 9.524]) vs the lowest tertile (1-69 mg/L). A low percentage decline during the first week of treatment was statistically significantly associated with a higher risk of poor outcome (logistic regression coefficient, 1.1; P = .009). At no point in time did CRP level predict the need for cardiac surgery.

High CRP level after 1 week of treatment and a slow percentage decline in CRP level during the first week of treatment are indicators of poor clinical outcome.