Three-year monitoring and comparison of results from two identical blood gas analyzers

Objectives: Measurement comparability between blood gas analyzers within a laboratory is of utmost importance. This study analyzed the data obtained from a three-year period. Design and methods: For quality monitoring one blood sample was tested on two identical blood gas analyzers at each of three shifts/day for three years. Deming regression analysis was used to determine result correlation and statistical identity between the two analyzers for pH, pCO(2), pO(2), sodium, potassium, chloride, ionized calcium, glucose, and lactate. Failures in the two-analyzer comparison were determined by the performance limits from the Institute of Quality Management in Healthcare (IQMH) and from the manufacturer respectively. Results: Correlation coefficients were greater than 0.96 (0.9622-0.9975) for all tested analytes. The measurements of every analyte on both analyzers were statistically identical. In the two-analyzer comparison failure numbers/1000 tests for pO(2) and glucose varied with the performance limits (IQMH: 0.6 and 49.2; the manufacturer: 19.3 and 4.4, respectively). In addition, persistent glucose failures (>5/week) between the two analyzers occurred occasionally. Conclusions: Results of all tested analytes between the two blood gas analyzers were interchangeable. Recurring glucose discrepancies might be a result of different lots of cartridges used on each analyzer, which were not identified during the initial installation.