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Stability and homogeneity of whole blood samples in CROQALM haematology scheme

BACKGROUND-AIM: The observed impact of the commercial control material on discrepancies between different instruments in hematology has encouraged the Croatian Centre for Quality Assessment in Laboratory Medicine (CROQALM) to improve hematology scheme by ensuring fresh blood for quality control. Because of its reduced stability it is very important to assure samples which are stable during analysis and homogenous across all prepared aliquots. The aim of the study was to show tested stability and homogeneity of homemade samples for CROQALM hematology scheme during 2016. METHODS: CROQALM hematology scheme is performed three times a year. Control sample for all rounds in 2016 was fresh blood from single donor with simulation of abnormal case in the second round by dilution. Donations, aliquots and testing were conducted in Croatian institute for transfusion medicine. Homogeneity and stability were tested on hematology analyzer (Ruby- Abbott/USA) for red blood cells (RBC), white blood cells (WBC) and platelets (PLT) according to ISO 13528:2005(E). Acceptance criteria for both homogeneity and stability was Ss ≤ 0.3*Q (Ss is between-samples standard deviation is standard deviation for proficiency testing based on CLIA Acceptable Test Performance Criteria. RESULTS: In three rounds during 2016 results of stability assessment have shown that the most unstable were WBC with stability varying from 48 to 72 hours. PLT were stable from 5 to 6 days and RBC 6 days. Stability was not altered when fresh sample was manipulated in order to simulate abnormal case. In all three cycles of CROQALM hematology scheme the homogeneity met the acceptance criteria. CONCLUSION: According to tested stability and in order to avoid impact of control material on participant’s results, samples must be delivered to all participants within 2 days after preparation and analyzed immediately upon receipt.

stability ; homogeneity ; whole blood ; control samples

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