Predictive Value of Leukocytosis and Neutrophilia for Bloodstream Infection

Abstract

Background Bloodstream infections are an important cause of morbidity and mortality in hospitalized adults. We sought to identify laboratory parameters predictive of blood culture-positivity. Methods We generated a database of patients having positive blood cultures during a 6-month period at our tertiary care community-based medical center. From this patient population, further instances of positive and negative blood culture were identified retrospectively (up to 60 months prior). Differences in laboratory parameters by culture result were studied. Results Of 766 blood cultures, 278 were positive, 395 were negative, and 93 were contaminated. Compared to patients with negative blood cultures, those with positive blood culture had significantly higher WBC count (15,160 ± 460 μl vs. 10,300 ± 200 μl), percent PMN (84.5 ± 0.6% vs. 77.9 ± 0.6%), absolute neutrophil count (12,950 ± 420 μl vs. 8200 ± 200 μl), and bandemia (8.5 ± 1.3% vs. 4.6 ± 0.9%; P = 0.0178). Calculated odds ratios (OR) for positive blood culture included WBC count ≥ = 12,000: OR = 3.16 (95% CI, 2.28–4.37); %PMN ≥ = 80: OR = 4.16 (95% CI, 2.89–5.98), and band PMN ≥ 5%: OR = 3.25 (95% CI, 1.59–6.64). Conclusion Presence of leukocytosis, neutrophilia, and bandemia is highly correlated with blood culture positivity (OR 4.26; 95% CI, 2.48–7.32; RR 49.5). Absence of these findings is inversely associated with blood culture positivity (OR 0.086; 95% CI, 0.044–0.17). A quantitative method of risk assessment is provided based on these parameters to expedite diagnosis and treatment of bloodstream infection.