Reliability of semiquantitative determination of procalcitonin serum concentrations in neonates

We studied the diagnostic usefulness of semiquantitative determination of procalcitonin (PCT) concentrations in neonatal serum by reference to a quantitative method. We compared 302 results of PCT measurements in 151 samples of venous blood collected during the 1st 7 days of life. The semiquantitative BRAHMS PCT-Q test and the quantitative immunoluminometric LUMItest were compared with Cohen's kappa as a measure of concordance. Concordance was revealed for 28.4% of samples, whereas 11.9% showed total disagreement. Concordance between both methods reached 88% when results from the next (lower or higher) category were included. The weighted kappa value was 0.235, indicative of satisfactory agreement between both methods. The semiquantitative BRAHMS PCT-Q test reveals satisfactory concordance with the quantitative method when results in the next category are included to account for readout error. The semiquantitative test is rapid, easy to use, and helpful as a supportive test when the quantitative assay is not available.