Hemolysis in laboratory samples is a frequent error that may lead to clinical misinterpretation and incorrect patient treatment. Thus, modern laboratory analyzers are able to assess the hemolysis index (HI). To prevent reporting of erroneous results, manufacturers are obliged to provide reliable HI threshold values. The aim of this study was to proof the quality of manufacturer’s given HI thresholds.

Methods

Dilution series with defined degrees of hemolysis were prepared by using blood samples from voluntary participants (n=77). In addition to the HI in each dilution, 18 measurands, namely sodium, potassium, chloride, aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), haptoglobin, total bilirubin, direct bilirubin, glutamate dehydrogenase (GLDH), creatine kinase (CK), iron, amylase, phosphate, total protein, enzymatic creatinine and high-sensitive troponin T, were measured on a cobas^®pro analyzer. Thresholds for maximum deviation of measurement results of 5 , 10 and 20 % were calculated. Then we determined cut-offs as the 5th percentile and median.

Results

Using potassium as an example we found HI thresholds at 57 (5th percentile) and 70 (median) with a corresponding result deviation of 5 % while the manufacturer HI threshold is given at 20. Thus, a higher HI threshold might be tolerated.

Conclusions

We established HI thresholds for 18 biochemistry assays. Eight assays showed considerable deviations of which six may have potential clinical relevance like potassium and high-sensitive troponin T. Optimizing thresholds can help to reduce the risk of unnecessary blocking of results and preventing considerably impaired results from being released.

Keywords: errors; hemolysis; hemolysis index (HI); laboratory testing; patient safety; preanalytical variability

Full text:

Evaluation of hemolysis index thresholds for 18 biochemistry assays: implications for laboratory-developed tests in the era of the IVDR