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Background: This study assessed the homogeneity and stability of control materials used in external quality assessment (EQA) of four coagulation tests, aiming to verify that these materials meet clinical testing requirements and to provide an evidence base for future improvement of laboratory coagulation test quality.
Methods: The homogeneity and stability of control materials were assessed according to the relevant guidance. Homogeneity assessment involved 10 vials of samples obtained from 2 batches (each vial tested twice). The homogeneity of control materials in four coagulation tests was assessed using one-way analysis of variance, with standard deviation of uniformity (Ss) ≤ 0.3 σ as an assessment criterion. Stability assessment involved two vials of sam-ples obtained from two batches (each vial tested twice). The stability of control materials was assessed at cold storage, room temperature, temperature of 37°C. Reconstitution stability of control materials placed in cold storage and at room temperature, and long-term stability of reconstituted control materials stored frozen (-20°C and -80°C) were observed. Linear regression analysis was performed to assess long-term stability.
Results: The Ss values of EQA control materials for four coagulation tests were PT L1 Ss = 0.084, PT L2 Ss = 0.889, APTT L1 Ss = 0.164, APTT L2 Ss = 0.223, Fbg L1 Ss = 6.256, Fbg L2 Ss = 2.251, TT L1 Ss = 0.552, TT L2 Ss = 0.3111. PT, APTT, Fbg, and TT were associated with the standard deviation of uniformity values of 0.3 σ. Non-reconstituted samples were observed at 37°C for 2 hours and 4 hours, and at room temperature for 1 day. Reconstituted samples were observed when stored at 4°C for 4 hours and 8 hours, at room temperature for 4 hours, and at -20°C and -80°C for 6 months. Instability of reconstituted samples was observed in PT and APTT tests at 4°C for 8 hours and at -20°C for 5 months.
Conclusions: EQA control materials presented with satisfactory homogeneity in four coagulation tests. Non-reconstituted samples presented with satisfactory stability at 37°C for 2 hours and 4 hours and at room temperature for 1 day, while reconstituted samples presented with satisfactory stability when refrigerated at 4°C for 4 hours, when kept at room temperature for 4 hours, and when frozen at -80°C for 6 months.
DOI: 10.7754/Clin.Lab.2020.200911
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