Comparison of the Creatinine in venous blood gas and formal laboratory (UEC)
Introduction:
Electrolyte readings for venous blood gases (VBG) have been used interchangeably with the electrolyte auto-analysers (UEC) in the emergency setting.
Objective:
To evaluate comparability between VBG and UEC readings (gold standard) in electrolytes – sodium and potassium
Methods:
21770 pathology records were retrospectively accessed with UEC and VBG matched within five minutes. We eliminated error readings and matched 16514 records for sodium and 16437 records for potassium. We underwent t-test analyses, calculating mean differences and correlation coefficients. Finally, we underwent subgroup analyses using pH to further assess comparability.
Results:
In examining the data, we noted that the VBG had a larger range of values in comparison to the UEC results. The standardised mean differences in all the groups noted were significant (P<0.001).
In all analyses sodium was consistently overestimated (MD >0.7) and potassium consistently underestimated (MD <-0.06) by the VBG. This gap widened in the acidic sodium and basic potassium group and narrowed in the basic sodium and acidic potassium groups.
With the exception of the K+ Acidic comparison, there was good correlation (r > 0.8) in both electrolyte groups.
Conclusion:
There are good positive correlations between VBG and UEC for sodium levels and potassium levels except for potassium in the acidic pH. Furthermore, mild assay adjustments could potentially reduce the mean differences.
As such, we recommend that sodium and potassium levels measurements be used interchangeably between the techniques with mild corrections. However, in the acidic pH setting, potassium levels should be used with caution in lieu of lower correlation.
