The Impact of Hemolysis-Index Thresholds on Plasma and Serum Potassium Measurements.

BACKGROUND: Modern clinical laboratory analyzers measure a hemolysis index (H-index) because test results can be inaccurate when intracellular contents from erythrocytes leak into serum or plasma. In 2020, Roche Diagnostics decreased the H-index from 90/100 to 20 for potassium, recommending that laboratories avoid using specimens with an H-index >20; however, there are a limited number of studies investigating the impact of this recommendation on patient testing.
METHODS: Out of 113 916 serum or plasma potassium tests performed within a 6-month interval, 72 patients with potentially hemolyzed potassium specimens (H-index >20) and a second non-hemolyzed specimen (H-index ≤20) within 2 h were identified. The clinical impact of decreasing the H-index and the utility of applying a corrective formula for adjusting potassium results were evaluated.
RESULTS: The majority of initial test results either had small differences between original and corrected results that would not have affected clinical management or H-indices above the threshold previously recommended by Roche. We estimated the second sample was reported an average of 3 h 23 min after the initial sample was collected, with 95% CI [2 h 37 min to 4 h 8 min], and the median time delay was 2 h 44 min.
CONCLUSIONS: Our analysis does not show a clear benefit from avoiding the use of potassium specimens above an H-index threshold of 20. Our findings suggest these practices may be detrimental in terms of patient safety due to increased turnaround time for a critical analyte. © American Association for Clinical Chemistry 2022. All rights reserved. For permissions, please email: journals.permissions@oup.com.