Prediction of Microbial Infection and Mortality in Medical Patients with Fever: Plasma Procalcitonin, Neutrophilic Elastase‐α‐Antitrypsin, and Lactoferrin Compared with Clinical Variables

Fever suggests the likelihood of severe microbial infection. Abnormal temperature, tachycardia, tachypnea, and abnormal white blood cell counts define the systemic inflammatory response syndrome (SIRS). In 300 hospitalized medical patients with fever, we determined clinical variables and procalcitonin, elastase-alpha1-antitrypsin, and lactoferrin levels in plasma. Of the patients, 71% had clinical infection (by clinical judgment) and 44% had microbial infection (by microbiological testing). SIRS occurred in 95%, and the 28-day mortality rate was 9%. The sensitivity for predicting microbial infection, bacteremia, and mortality was less but the specificity was greater for supranormal procalcitonin, elastase-alpha1-antitrypsin, and lactoferrin levels than for SIRS. The area under the receiver operating characteristic curve (AUC) for microbial infection was higher for procalcitonin and elastase-alpha1-antitrypsin levels than for clinical variables and lactoferrin level. The AUC for bacteremia was also higher for inflammatory factors (>0.70; P < .001) than for clinical variables. The AUC for mortality (P < .05) was 0.79 for the respiratory rate, 0.69 for elastase-alpha1-antitrypsin level, 0.65 for heart rate, 0.61 for procalcitonin level, and 0.60 for white blood cell count. In febrile medical patients, plasma procalcitonin and elastase-alpha1-antitrypsin levels may predict microbial infection and bacteremia better than (and mortality as well as) do clinical symptoms.