A-137 Stability of Analytes in Uncapped Specimens

Abstract Background Traditionally, analyte stability is tested on the capped specimens. Routine workflow may require sharing uncapped specimens between multiple analyzers. This study was conducted to determine the impact of storing uncapped specimens on stability of analytes in the Comprehensive Metabolic Panel (CMP) tested on Beckman Coulter AU5800 analyzer. Methods Serum from patient specimens (SST® tubes) were mixed to prepare 5 sets of pooled patients’ specimens (PPS), aliquoted (2.5 mL) and capped. The 5 PPS were uncapped, analytes tested in duplicate at baseline (0 hr); 5 hr (reflecting more than the expected duration); 21 hr and 27 hr (reflecting 2 extreme times to identify a failure point). Averaged results were used for time-point comparisons. The absolute and percent differences vs 0 hr were compared to the respective total allowable error (TEA)1, index values calculated and averaged for 5 PPS: Absolute TEA Index = (Absolute Difference / Absolute TEA) × 100 %TEA Index = (% Difference / % TEA) × 100 Storage duration that showed both the absolute and %TEA index values 33.3 was considered to introduce substantial error in test results. Results Table 1 highlights the analytes that showed substantial error: At 21 hours: Creatine kinase, Carbon dioxide and Sodium. At 27 hours: Creatine kinase, Carbon dioxide, Chloride, Potassium and Sodium. Conclusions The results of the study demonstrate that extreme storage in uncapped tubes up to and greater than a day substantially affected only 5 of 19 test results in the CMP. More importantly, none were substantially affected at 5 hr. It is imperative that the laboratories conduct studies to determine the impact of storage conditions of uncapped samples on test results. Reference: 1. Clinical Laboratory Improvement Amendments of 1988 Proficiency Testing Regulations Related to Analytes and Acceptable Performance. Federal Register, Vol. 87, 131,2022.