The Effect of Repeated Versus Initial Procalcitonin Measurements on Diagnosis of Infection in the Intensive Care Setting

Procalcitonin (PCT) measurement has been proposed to direct antibiotic use. We examined whether repeated PCT measurements (0, 6, and/or 12 hours) versus the initial measurement only (time 0) increased the sensitivity and specificity of PCT for diagnosing infection in intensive care unit patients. Infection was identified in 67/176 (38%) patients. The sensitivity of repeated versus the initial PCT measurement (with a cutoff value 0.5 ng/mL) was 52/67 (77%; 95% confidence interval [CI], 66%-87%) vs 46/67 (69%; 95% CI, 56%-79%; P = .04) and specificity 60/109 (55%; 95% CI, 45%-65%) vs 59/109 (54%; 95% CI, 44%-64%; P = 1.0). Repeat PCT evaluations over 12 hours did not provide a clinically significant improvement in diagnostic accuracy when compared to the initial single test.