Definition of icteric interference index for six biochemical analytes

Abstract

IntroductionIcterus, if not detected, can affect the validity of results delivered by clinical laboratories, leading to erroneous results. This study aims to define bilirubin interference for some biochemical analytes and compare it with the manufacturer’s data. Material and methodsSerum pools prepared with outpatients’ samples were spiked with increasing bilirubin concentration (Merck, reference14370, Darmstadt, Germany) up to 513 µmol/L in order to evaluate the bias for the following biochemical analytes: creatinine (CREA), creatine kinase (CK), cholesterol (CHOL), gamma-glutamyltransferase (GGT), high-density lipoprotein cholesterol (HDL), and total protein (TP). For each analyte, six pools of different concentrations were prepared. Measurements were made employing Cobas 8000 analyser c702-502, Roche Diagnostics (Mannheim, Germany). This study employed a study procedure defined by the Spanish Society of Laboratory Medicine. ResultsObtained bilirubin concentrations producing a negative interference were 103 µmol/L for CHOL, 205 µmol/L for TP and 410 µmol/L for CK, but only for CK values less than 100 U/L. Bilirubin concentrations lower than 513 µmol/L do not produce interference for HDL and GGT. Finally, for the studied bilirubin concentrations, there is no interference for CREA higher than 80 µmol/L. ConclusionIcterus interferences have been defined for each analyte, observing differences compared to data provided by the manufacturer. The evidence indicates that each laboratory should evaluate icteric interferences to ensure the high quality of the delivered results, thus benefiting patient care.

Preanalytical Errors in Clinical Laboratory Testing at a Glance: Source and Control Measures

“…Other forms of deterioration of sample quality are icteric and lipemic changes. Bilirubin in icteric samples interferes with peroxidase-coupled reactions, causing a falsely low glucose, cholesterol, triglyceride, and uric acid measurement [6]. Lipemia is defined as turbidity in a sample caused by the accumulation of lipoproteins, mainly very-low-density lipoproteins (VLDL) and chylomicrons.…”

“…It causes an increase in the solid phase relative to the water phase component in the patient's serum samples, leading to pseudo hyponatremia, which occurs mainly in the indirect ion-selective electrodes (ISE) measurement method [7]. Additionally, some biochemistry analytes such as creatinine, potassium, sodium, chloride glucose, direct bilirubin, and urea will give variable results due to spectral interference and volume displacement effect of lipemia [6,8].…”

“…Records of the HIL index assist in communication with the requesting clinician [8]. The clinician should note the detection of an icterus sample earlier as a caution for potential result inaccuracy [6]. Unlike hemolyzed and icteric samples, lipemic samples can be further processed using high-speed or ultracentrifugation to obtain clear serum for analysis.…”