Interference from endogenous substances is one of the leading source of errors clinical laboratories encounter at the pre-analytical phase of testing. Automated chemistry platforms allow accurate measurement of interferences due to endogenous substances such as hemolysis, icterus and lipemia utilizing semi-quantitative testing with indices.
Experts from Medpace’s central laboratory evaluated the effect of hemolysis, icterus and lipemia on chemistry assays and assessed the association between the amount of interfering substances and ordinal values reported by the automated chemistry analyzer as H-, I- and L-indices. They presented their findings at the 70th AACC Annual Scientific Meeting & Clinical Lab Expo in Chicago a few months ago. Details about the poster presentation are below. You can read the entire paper and view the scientific poster here.
Authors: Neval Akbas PhD, Bryan Eppert PhD, Judy Miller, Catherine Schulten, Cynthia Wallace and Traci Turner MD
Three normal serum pools were prepared and supplemented with six increasing concentrations of hemolysate, bilirubin and triglyceride. These samples were then tested for 40 chemistry analytes for hemolysis, 38 chemistry analytes for icterus and 31 chemistry analytes for lipemia interferences on a Beckman Coulter AU5800 series analyzer. Results were compared to baseline values and acceptability of results were determined based on the total allowable error limits according to CAP and CLIA guidelines. Analytes showing a bias more than ±10% for lipemia were airfuged and reanalyzed. The amount of hemolysis, icterus and lipemia were measured using a semi-quantitative photometric test on the same instrument using the Beckman Coulter LIH reagent system. These values were assigned by the instrument on an ordinal scale as qualitative flag levels (“N”, “+”, “++”, “+++”, “++++” and “+++++”) to reflect the degree of hemolysis, icterus and lipemia in a specimen. Visual detection of the hemolysis, icterus and lipemia was also performed independently on each aliquot in a blinded manner by three experienced technologists.
Interference from hemolysis was detected for 20 of 40 tested analytes. Half of these twenty analytes were affected by gross hemolysis at hemoglobin concentrations of 798 mg/dL with ordinal values of “+++++” flag level. Only three analytes (aspartate aminotransferase, direct bilirubin and lactate dehydrogenase) were affected by slight hemolysis at hemoglobin concentrations of 76 mg/dL with ordinal values of “+” flag level. Aldolase was the only analyte that was affected at hemoglobin concentrations of 25 mg/dL. Interference from icterus was detected for 9 of 38 tested analytes. Three of these nine analytes were affected by gross icterus at bilirubin concentrations of 60 mg/dL with ordinal values of “+++++” flag level. Free glycerol was the only analyte that was affected by bilirubin concentrations of 3.7 mg/dL with ordinal values of “+” flag level. Interference from lipemia was detected for 9 of 31 tested analytes. There was no analyte that was affected by triglyceride concentrations of 300 and 600 mg/dL with ordinal values of “+” and “++” flag levels. BUN was the only analyte that was affected by gross lipemia at triglyceride concentrations of 2100 mg/dL with ordinal values of “+++++” flag level. Visual inspection results for hemolysis and lipemia showed good agreement between three technologists and were consistent with the corresponding ordinal values. Visual inspection results for icterus showed more variations between technologists and compared to ordinal values.
We have demonstrated that some of the chemistry analytes were affected by hemolysis, icterus and lipemia interferences. Generally, our results were consistent with manufacturer’s claims. Our laboratory applied the results to determine the cut-off indices for hemolysis, icterus and lipemia on tested chemistry analytes using the robust measurement of the interferent provided by the automated chemistry analyzer. The implementation of the indices allows us to effectively determine the specimen integrity and prevent erroneous test results due to hemolysis, icterus and lipemia.