Could calprotectin and pentraxin 3 be measured in cerebrospinal fluid – a verification study

Objectives Calprotectin and pentraxin 3 (PTX3) have emerged as potential biomarkers of central nervous system inflammatory diseases, yet evidence based analytical verifications in cerebrospinal fluid (CSF) is lacking. This study aimed to verify the manufacturer’s claims for precision, limit of quantitation (LoQ) and stability for calprotectin using fCAL turbo reagent (Bühlmann Laboratories AG, Schonenbuch, Switzerland); precision and linearity for PTX3 using Human PTX3 ELISA Kit (BioVendor Group, Brno, Czech Republic) in CSF. Methods Samples were collected in additive-free tubes and centrifuged at 400 g, 10 min. Calprotectin was measured on Atellica Solution analyser (Siemens), PTX3 was determined by ELISA method on the Thunderbolt analyser (Gold Standards Diagnostics). The verification protocol was carried out according to Clinical and Laboratory Standards Institute (CLSI) guidelines: precision by EP15-A3, LoQ verification by EP17-A2, and linearity by EP6-A. Calprotectin stability at −20 °C for 7 days was assessed in three CSF samples. Results The CV%s for calprotectin precision were 4.52 % and 1.66 %; for PTX3 were 6.0 % and 8.9 %, respectively. The declared LoQ for fCAL turbo of 50.0 μg/L (CV%<20 %) was verified. The stability equation for calprotectin did not exceed the MPD (41.6 %), and it was y=−0.15× (95 % Cl −0.49 to 0.19), indicating stability at −20 °C for 7 days. The method for PTX3 was linear over the manufacturer declared ranges (3,212.0–406.0 and 3,315.0–411.0 ng/L). Conclusions This study showed that Bühlmann fCAL turbo reagent and the Biovendor Human PTX3 ELISA kit support the determination of calprotectin and PTX3 in CSF for research purposes, with potential future clinical applications.