Quantitative versus Semiquantitative Procalcitonin Measurement

Abstract

Background: Procalcitonin, an excellent marker of sepsis, is measured in trauma intensive care units by a standard quantitative test. Recently, a quicker semiquantitative test has become available. The aim of this study was to compare both tests to determine whether the quicker new test is as reliable as the standard test for trauma patients. Patients and Methods: This prospective 4-month study included all severely traumatized patients admitted to our intensive care unit. Parallel procalcitonin measurements were performed daily, comparing the standard LUMItestPCT® to the categorization (normal 2 ng/ml) by the quicker PCT-Q® test (both B.R.A.H.M.S.-Diagnostica GmbH, Henningsdorf, Germany). Results: Procalcitonin was measured in 167 samples from 15 patients (Injury Severity Score 29 ± 13). Among the increased procalcitonin levels (increased LUMItest-PCT®), the PCT-Q® test picked up only 14 of 38 samples (36.8%). Among the normal procalcitonin levels (normal LUMItestPCT®) the PCT-Q® test classified 127 of 129 samples (98.4%) the same, i.e. correctly, and two samples (1.6%) moderately increased, i.e. too high. Compared to the LUMItestPCT®, the PCT-Q® test has a low sensitivity of 44% and a high specificity of 97%. Conclusions: The semiquantitative PCT-Q® test is highly specific but far less sensitive than the LUMItestPCT®. Normal procalcitonin readings by the PCT-Q® test are often incorrectly low, while moderately (0.5–2 ng/ml) and highly increased (> 2 ng/ml) readings are usually correct. Because of the rate of incorrectly low readings, the PCT-Q® test is unreliable for trauma patients.