Definition of icteric interference index for six biochemical analytes

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Analytical Biochemistry

Background:

• Icterus, characterized by elevated bilirubin levels, can significantly impact the accuracy of clinical laboratory results.
• Undetected icterus may lead to erroneous diagnostic and therapeutic decisions, compromising patient care.
• Standardized interference data from manufacturers may not always reflect real-world clinical scenarios.

Purpose of the Study:

• To quantitatively define bilirubin interference thresholds for key biochemical analytes.
• To compare experimentally determined interference levels with manufacturer-provided data.
• To emphasize the importance of in-house validation of interference in clinical laboratories.

Main Methods:

• Serum pools from outpatients were spiked with increasing concentrations of bilirubin up to 513 µmol/L.
• Interference was evaluated for creatinine (CREA), creatine kinase (CK), cholesterol (CHOL), gamma-glutamyltransferase (GGT), high-density lipoprotein cholesterol (HDL), and total protein (TP).
• Measurements were performed using a Cobas 8000 analyser (Roche Diagnostics), following a protocol by the Spanish Society of Laboratory Medicine.

Main Results:

• Negative interference occurred at 103 µmol/L for cholesterol, 205 µmol/L for total protein, and 410 µmol/L for creatine kinase (for values <100 U/L).
• High-density lipoprotein cholesterol and gamma-glutamyltransferase showed no interference below 513 µmol/L.
• Creatinine showed no interference at concentrations above 80 µmol/L within the studied range.

Conclusions:

• Experimentally determined bilirubin interference levels differ from manufacturer data for several analytes.
• Laboratories must independently assess icteric interferences to guarantee the reliability of test results.
• Proactive evaluation of bilirubin interference is crucial for maintaining high-quality laboratory diagnostics and improving patient outcomes.