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

Measurement comparability between blood gas analyzers within a laboratory is of utmost importance. This study analyzed the data obtained from a three-year period.

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, pCO₂, pO₂, 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.

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 pO₂ 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.

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.