Verification of Assayed Blood Gas Quality Control Ranges

Blood gas quality control (QC) is an essential and mandatory part of a laboratory's quality plan. The acceptable QC range should be 2 SD from the mean value. The use of assayed QC material does not negate the responsibility of the laboratory to calculate the mean and 2 SD ranges of QC measurements for verification. Verifying assayed QC ranges is a Clinical Laboratory Improvement Amendment (CLIA) requirement. This study shows the results of assayed QC mean and 2 SD range verification from a blood gas analyzer.

QC data from a blood gas analyzer were compared to manufacturer-provided mean and ranges. The percent difference between the measured mean and the manufacturer-provided mean was calculated to assess agreement. The measured SD was used to determine how many SD the manufacturer-provided ranges were from the measured mean.

The largest difference in mean values was 2.27% > the manufacturer-provided mean. Forty-eight percent of all mean value comparisons showed a difference of 0%, and 71% were < 1%. The manufacturer-provided ranges were considerably wider than the measured 2 SD range, ranging from 2.4-75 SD. None of the manufacturer-provided ranges were deemed acceptable for clinical use.

Our analysis validates the CLIA mandate and American Association for Respiratory Care Clinical Practice Guideline recommendation that laboratories must verify manufacturer-provided QC means and ranges and adjust QC means and ranges to match the performance of their blood gas analyzer.