Effect of leukocytosis at initial examination on prognosis in patients with primary unstable angina

Background: Leukocytosis with acute myocardial infarction at initial examination predicts adverse prognosis, but it is unknown whether it predicts outcome in patients with primary unstable angina. Methods and Results: We studied 414 consecutive patients with unstable angina admitted through the emergency department to telemetry and intensive care units of an urban academic hospital. To study primary unstable angina, we excluded 134 patients with precipitants (eg, urosepsis, pneumonia) that may cause leukocytosis. Of 280 patients, 96 (34%) had leukocytosis (leukocyte count > 10,000 per μL) at initial examination. A total of 30 patients (11%) died and 47 (17%) died or had nonfatal myocardial infarction within 12 months of initial examination. In a univariate Cox model, patients with leukocytosis had a hazard ratio (HR) of 2.6 (95% confidence interval [CI] 1.3-5.4) for death by 1 year. In a multivariate Cox model the only significant predictors of 1-year death were congestive heart failure at initial examination (HR 7.8; 95% CI 2.8-22) and elevated creatinine (HR 2.7; 95% CI 1.3-5.7); in this model, the relation between leukocytosis and prognosis was markedly attenuated (HR 1.4; 95% CI 0.6-2.9). The adjusted HR for leukocytosis was 1.3 (95% CI 0.72.3) for death or nonfatal MI by 1 year. Conclusions; Leukocytosis at initial examination is associated with adverse prognosis in patients with primary unstable angina. However, the association is confounded by other important predictors of prognosis. Leukocytosis may be a marker of stress associated with more severe cases of unstable angina or comorbid conditions.