Rajeevan Selvaratnam

Objectives Hemolysis, icterus, and lipemia (HIL) are common sources of endogenous interference in clinical laboratory testing. Defining the threshold of interference for immunoassays enables appropriate reporting of their results when they are affected by HIL. Methods Pools of residual patient serum samples were spiked with a known amount of interferent to create samples with varying concentrations of hemolysate, bilirubin, and Intralipid that mimicked the effects of endogenous HIL. Samples were analysed on the Alinity i analyser (Abbott Diagnostics) for more than 25 immunoassays. The average recovery relative to the non-spiked sample was calculated for each interference level and was compared to a predefined allowable bias. Results C-peptide, estradiol, serum folate, free T4, homocysteine, insulin, and vitamin B12 were found to be affected by hemolysis, at hemoglobin concentrations between 0.3 to 20 g/L. Immunoassays for BNP, estradiol, free T3, and homocysteine were affected by icterus at conjugated bilirubin concentrations between 50 to 1,044 μmol/L. BNP, serum folate, and homocysteine were affected by Intralipid with measured triglyceride concentrations between 0.8 to 10 mmol/L. Lastly, serological immunoassays for HIV and hepatitis A, B and C were also affected by interferences. Conclusions Immunoassays are impacted by varying degrees of HIL interference. Some measurands, in the presence of interference, are affected in a manner not previously indicated. The data presented herein provide an independent evaluation of HIL thresholds and will be of aid to resource-limited clinical laboratories that are unable to internally verify endogenous interferences when implementing the Alinity i analyser.