Elevated procalcitonin is associated with increased mortality in patients with scrub typhus infection needing intensive care admission

Context: Procalcitonin is a biomarker of bacterial sepsis. It is unclear if scrub typhus, a rickettsial illness, is associated with elevated procalcitonin levels. Aim: To assess if scrub typhus infection is associated with high procalcitonin levels and whether high levels portend a poorer prognosis. Setting and Design: Retrospective study of patients with severe scrub typhus infection, admitted to the medical intensive care unit of a tertiary care university affiliated teaching hospital. Materials and Methods: Eighty-four patients with severe scrub typhus infection that also had procalcitonin levels were assessed. Statistical Analysis: Relationship between procalcitonin and mortality explored using univariate and multivariate analyses. Results: The mean (±standard deviation) age was 40.0 ± 15.5 years. Patients were symptomatic for 8.3 ± 4.3 days prior to presentation. The median admission procalcitonin level was 4.0 (interquartile range 1.8 to 8.5) ng/ml; 59 (70.2%) patients had levels >2 ng/ml. Invasive mechanical ventilation was required in 65 patients; 20 patients died. On univariate analysis, admission procalcitonin was associated with increased odds of death [odds ratio (OR) 1.09, 95% confidence interval (CI) 1.03 to 1.18]. On multivariate logistic regression analysis including procalcitonin and APACHE-II score, the APACHE-II score was significantly associated with mortality (OR 1.16, 95% CI 1.06 to 1.30, P = 0.004) while a trend was observed with procalcitonin (OR 1.05, 95%CI 1.01 to 1.13, P = 0.09). The area under the receiver operating characteristic (ROC) curve, AUC, for mortality was 0.77 for procalcitonin and 0.78 for APACHE-II. Conclusions: Procalcitonin is elevated in severe scrub typhus infection and may be associated with higher mortality.