Determining procalcitonin at point-of-care; A method comparison study of four commercial PCT assays

OBJECTIVE: Procalcitonin (PCT) testing adds value in the early detection of infection and sepsis, as well as in management of antibiotic therapy. We determined the analytical and diagnostic performance of four PCT assays at POC. METHODS: PCT assays on AQT90 FLEX, Getein 1100, mLabs, and Finecare POC analyzers, in whole blood and plasma, were analyzed for repeatability, linearity, accuracy and concordance, by comparing with our reference PCT assay on the Cobas E602 system. RESULTS: For all assays precision was found higher in plasma than in whole blood. AQT90 showed good performance in all analytical and diagnostic areas, irrespective of test matrix and PCT concentration. The other POC assays demonstrated at least one analytical weakness. The Getein assay showed adequate precision only in plasma at high PCT levels, the mLabs assay only in plasma at low PCT levels. Accuracy, as demonstrated by Bland-Altman and Passing-Bablok analysis, was found adequate only for the AQT90 FLEX and Getein 1100 assay. Diagnostic concordance at 0.5 ​ng/mL was found excellent for the AQT90 FLEX, Getein 1100, and Finecare assays, much lower for the mLabs assay. At 0.25 ​ng/mL, only the AQT90 FLEX and Finecare assays showed excellent concordance with the reference assay. CONCLUSIONS: The AQT90 FLEX PCT assay demonstrated excellent analytical performance and diagnostic agreement with the Cobas E602 assay, allowing both stand-alone and side-by-side testing. The other assays demonstrated some analytical deficiencies, potentially limiting their diagnostic use. Any clinical use of PCT results should always be in combination with all other clinical signs and diagnostic information.