Exploratory Study on Reference Intervals of Calprotectin and Pentraxin 3

Introduction: The aim of our study was to determine reference intervals for serum pentraxin 3 and calprotectin, as well as for urine calprotectin according to the CLSI EP28-A3C guidelines for defining, establishing, and verifying reference intervals in the clinical laboratory. Materials and methods: A total of 120 serum and urine samples from either healthy volunteers or outpatients were used for reference interval establishment. The participants had CRP levels, leukocyte counts, serum urea levels, creatinine levels, and estimated glomerular filtration rates (CKD-EPI eGFRs) within the reference range and no medical history of acute/chronic inflammatory diseases/conditions or cancer. Calprotectin was measured via a commercially available turbidimetric method – the Bühhlmann fCAL® Turbo Reagent Kit – while pentraxin 3 was measured using the Human Pentraxin 3 ELISA Kit from the BioVendor Group. Results: The serum calprotectin reference range was ≤ 3.6 mg/L, the 90% CI for the upper reference range was 3.1-4.1 mg/L, while the serum pentraxin 3 reference concentration was ≤ 3.0 µg/L, and the 90% CI for the upper reference range being 2.7-3.2 µg/L. Additionally, the urinary calprotectin concentration was ≤ 1.4 mg/L, with a 90% CI for the upper reference range of 1.0-1.7 mg/L. Conclusion: This study reports sample and method-specific reference intervals for the detection of various inflammatory conditions.