Verification of harmonized reference intervals in Croatia: is it time for a change?

Introduction:The study of harmonized reference intervals (RIs) in Croatia was published in 2004.Since then, notable methodology and population characteristics changes have occurred in the Croatian population, highlighting the need for re-evaluation.This study aimed to verify harmonized RIs for hematology, coagulation, and clinical chemistry laboratory tests and assess their applicability in one clinical hospital center.Materials and methods: This verification study included 100 apparently healthy adults (40 males, 60 females; aged 22 to 75 years), selected using both a priori and a posteriori exclusion criteria following CLSI EP28-A3c guidelines.Blood samples were collected under standardized preanalytical conditions.Hematology analysis was performed on the Sysmex XN1000 analyzer (Sysmex, Kobe, Japan), coagulation testing on the Sysmex CS2500 analyzer (Siemens Healthcare Diagnostics Inc., Marburg, Germany), and clinical chemistry analysis on the Beckman Coulter DxC700AU (Beckman Coulter, Brea, USA) and Radiometer ABL90 FLEX (Radiometer, Brønshøj, Denmark) analyzers.Reference intervals were considered verified if at least 90% of results (18/20) fell within the predefined RIs.Results: All tested hematology and coagulation RIs were successfully verified.Among 27 tested biochemical analytes, 25 RIs were verified in the first sample set.Total calcium and alkaline phosphatase RIs required additional verification.International harmonized RIs were adopted and successfully verified for both tests using two independent sample sets.Conclusions: Most harmonized RIs in use in Croatia remain applicable to the adult population of one clinical hospital center.However, periodic re-evaluation is needed due to changes in analytical methods and population characteristics.Reference intervals from international harmonization projects can provide a valid alternative when local verification fails.