Leukocyte count in peripheral arterial disease: A simple, reliable, inexpensive approach to cardiovascular risk prediction

Background: An elevated leukocyte count is widely proven to predict cardiovascular risk in healthy subjects and coronary patients, but its prognostic role in peripheral arterial disease (PAD) has received scarce attention. Objectives: To assess the impact of leukocyte count on the incidence of major cardiovascular events in PAD, and verify whether it adds to the prognostic power of the ankle/brachial index (ABI). Methods: The occurrence of myocardial infarction and stroke was prospectively assessed in 259 consecutive PAD patients. Receiver-operating characteristic analysis and the bootstrap approach were used to identify the best cut-offs to predict the outcome, and hazard ratios (HRs) and c-statistics to assess the ability to classify risk. Results: During a median follow-up of 30.0 months, 28 patients had an event. Adjusted Cox analyses performed on total and differential leukocyte counts, showed that only total leukocyte count (TLC) and neutrophil count (NC), considered as continuous variables, were associated with increased cardiovascular risk (HR = 1.35, p < 0.01 and HR = 1.31, p < 0.02, respectively). Patients with ABI <= 0.63 plus TLC > 7.7 x 10(9)/L or NC>4.6 x 10(9)/L had a higher risk of about 5-fold vs patients with ABI > 0.63 plus TLC <= 7.7 x 10(9)/L (p < 0.01) or NC <= 4.6 x 10(9)/L (p < 0.01). The c-statistic for ABI was 0.61, similar to those for TLC (0.63) and NC (0.66). However, it significantly increased to 0.70 and 0.69 for the models incorporating ABI and TLC or ABI and NC, respectively (p < 0.05 for both vs ABI alone). Conclusions: TLC and NC, which are inexpensive and reliable tests, predict major cardiovascular events in PAD, and add to the prognostic power of ABI, currently the most powerful prognostic indicator in these patients. (C) 2009 Elsevier Ireland Ltd. All rights reserved.