부산대학교 도서관

Background: The use of point-of care (POC) assays to monitor hemoglobin A1C (HbA1C) is widely practiced and can result in enhanced glycemic control. POC HbA1C testing performed at our hospital's diabetes clinic is regulated through the College of American Pathologists (CAP), which requires participation in proficiency testing (PT). However, POC HbA1C testing at our affiliated ambulatory clinics, like the vast majority of ambulatory clinics in the US that run waived tests, is not regulated by CAP. Objective: We aimed to analyze the long-term performance of the DCA Vantage, one of the most commonly used HbA1C POC devices, as operated by certified medical technologists or end-user operators (nurses) at our hospital's diabetes clinic and to initiate PT at our affiliated ambulatory clinics for POC HbA1C using frozen patient samples. Methods: To assess long-term performance of the DCA Vantage analyzer operated by a certified medical technologist, we compared results obtained by the POC device to results obtained by our laboratory-based HPLC method over a period of 32 months using 127 fresh patient samples. Performance of DCA Vantage in the hands of end-users (nurses) was assessed by comparing results from the last three years of CAP PT surveys to assigned NGSP values and to peer mean values. Stability of HbA1C in frozen patient samples, as it pertains to PT setting in the ambulatory clinics, was evaluated by measuring HbA1C in six deidentified, discarded whole blood patient samples before and after samples were aliquoted into small Eppendorf tubes, stored frozen at –20° for one month, and allowed to thaw at room temperature for eight hours. Results: Deming regression analysis showed good long-term agreement between POC results obtained by medical technologist and HPLC results, with an r2 value of.9547 and the following relationship: POC = 1.016(HPLC) – 0.01485. Total bias was 0.09%. Positive assay bias was apparent at all levels; however, significantly higher bias was observed at high HbA1C levels. Comparing CAP PT results at our diabetes clinic to the assigned NGSP values and peer mean values revealed good agreement with an r2 value of.9849 and.9922, and a bias of 0.11% and 0.20%, respectively. Deming regression showed the following relationships: PT results = 1.064(NGSP) – 0.3772 and PT results = 1.039(peer mean) – 0.1011. HbA1C was stable in frozen patient samples with percent difference ranging between –3.4% and –9.3% across the tested concentration range. Conclusion: Long-term performance of the DCA Vantage analyzer for the measurement of HbA1C is good whether operated by certified laboratory personnel or non-laboratory personnel. Frozen patient samples are suitable to be used as PT specimens as an alternative to external PT program specimens. Using PT specimens with a wide concentration range is recommended due to the higher assay bias at high HbA1C levels. [ABSTRACT FROM AUTHOR]