Demonstrating the feasibility of accurately and reliably correcting potassium results for mildly hemolytic samples...

For several decades, there has been an ongoing debate about the appropriateness and reliability of correcting potassium concentration results for hemolyzed samples. As part of implementing a new Roche Cobas Pro analyzer system the possibility of correcting potassium results in hemolytic samples using a new, thorough experimental design, was investigated.

The relationship between hemolytic index (HI) and increases in potassium concentration was studied by performing a linear regression on hemolysate dilution series (HI 0-160 mg/dL) from 20 left-over patient samples. The obtained correction procedure was validated using another 20 left-over patient samples. Corrections were accepted according to a correction concordance of 100% within the total allowable error criterion of 4.85%.

The obtained reporting procedure was: HI 0-17 quantitative potassium reporting, HI 18-100 correct potassium for HI, and report as text including a disclaimer for in vivo hemolysis; samples were rejected for HI > 100. In the validation cohort, 70/70 samples eligible for correction were within the TEa criterion. The maximum negative and positive errors were -2.8% and 2.9%, respectively.

Correcting potassium concentration results in a designated HI range is feasible and increases the accuracy the potassium results in samples with mild in vitro hemolysis.