Diagnostic accuracy of procalcitonin in critically ill immunocompromised patients

This prospective, observational study included patients with suspected sepsis. Patients were classified into one of three diagnostic groups: no infection, bacterial sepsis, and nonbacterial sepsis.We included 119 patients with a median age of 54 years (interquartile range [IQR], 42-68 years). The general severity (SAPSII) and organ dysfunction (LOD) scores on day 1 were 45 (35-62.7) and 4 (2-6), respectively, and overall hospital mortality was 32.8%. Causes of immunodepression were hematological disorders (64 patients, 53.8%), HIV infection (31 patients, 26%), and solid cancers (26 patients, 21.8%). Bacterial sepsis was diagnosed in 58 patients and nonbacterial infections in nine patients (7.6%); 52 patients (43.7%) had no infection. PCT concentrations on the first ICU day were higher in the group with bacterial sepsis (4.42 [1.60-22.14] vs. 0.26 [0.09-1.26] ng/ml in patients without bacterial infection, P < 0.0001). PCT concentrations on day 1 that were > 0.5 ng/ml had 100% sensitivity but only 63% specificity for diagnosing bacterial sepsis. The area under the receiver operating characteristic (ROC) curve was 0.851 (0.78-0.92). In multivariate analyses, PCT concentrations > 0.5 ng/ml on day 1 independently predicted bacterial sepsis (odds ratio, 8.6; 95% confidence interval, 2.53-29.3; P = 0.0006). PCT concentrations were not significantly correlated with hospital mortality.Despite limited specificity in critically ill immunocompromised patients, PCT concentrations may help to rule out bacterial infection.Procalcitonin (PCT), a peptide composed of 116 amino acids, is normally produced by the C cells in the thyroid gland. Because PCT is cleaved in the gland by a specific protease, circulating levels are very low (< 0.1 ng/ml) in healthy individuals. Serum PCT elevation in patients with bacterial sepsis was first reported in 1993 [1]. Over the last decade, PCT has gained ground as an early marker for bacterial sepsis in emergency departments and intensive care units