Hemolysis, Icterus, and Lipemia Interference Limits for Serum β-hydroxybutyrate Testing

Measurement of β-hydroxybutyrate (BOHB) is a valuable tool for the assessment of metabolic acidoses. In this study we evaluated hemolysis, icterus, and lipemia interference thresholds for a commonly used BOHB assay, the Stanbio β-Hydroxybutyrate LiquiColor reagent, on 3 different Roche cobas analyzers.

Remnant patient samples were combined to generate pools with target BOHB concentrations of approximately 0.20, 3.00, and 7.00 mmol/L into which increasing amounts of hemolysate, bilirubin, or Intralipid® were added. Samples were measured in triplicate for both interferences and BOHB concentration on Roche cobas c502, c501, and c311 analyzers.

We determined that the Stanbio β-Hydroxybutyrate LiquiColor reagent will tolerate hemolysis to a hemolysis index of 400 (approximately 400 mg/dL hemoglobin) for BOHB concentrations ≤1.00 mmol/L, or 1010 for BOHB concentrations of >1.00 mmol/L. For icterus, the assay was unaffected by bilirubin to an icterus index of 25 [approximately 25 mg/dL bilirubin (427 μmol/L)] for all concentrations tested. Using the most conservative data from our study, the lipemia index limit was set at 800.

Our studies across 3 laboratories running 3 different cobas modules allowed our health system to better define permissible limits of sample quality and these updated values will reduce the number of unnecessary cancelations as compared to the limits defined by the manufacturer. Our data also demonstrated heterogeneity of interference between analyzer models, which is an important consideration for those seeking to adopt the limits determined on analyzers other than those in their own laboratories.