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"Direct" and total bilirubin tests: contemporary problems
1Department of Pathology, Ohio State University, Columbus 43210-1240.
Clinical Chemistry
|April 1, 1993
Summary
Direct-reacting bilirubin (DBIL) assays show significant variability and bias across laboratories. Key issues include calibration, lack of serum blanks, and reagent problems, impacting accuracy in clinical diagnostics.
Area of Science:
- Clinical Chemistry
- Laboratory Medicine
- Diagnostic Assays
Background:
- Direct-reacting bilirubin (DBIL) measurements are crucial for diagnosing conditions like neonatal jaundice.
- Previous studies indicated variability in bilirubin assays, necessitating further investigation into DBIL specific challenges.
Purpose of the Study:
- To identify and analyze the causes of significant variability and bias in direct-reacting bilirubin (DBIL) assays.
- To compare DBIL assay performance with total bilirubin (TBIL) and reference methods.
Main Methods:
- Analysis of results from eight College of American Pathologists Comprehensive Chemistry Survey challenges over three years.
- Review of manufacturer information regarding DBIL assay methodologies.
Main Results:
- High variability and significant bias were observed in DBIL results among major peer groups compared to a reference method.
- Total bilirubin (TBIL) assays demonstrated better agreement among peer groups and with the reference method.
- Within-group precision (SD) for DBIL was generally acceptable, indicating bias as the primary source of error.
Conclusions:
- Major causes of DBIL assay variability include calibration issues, absence of serum blank measurements, inadequate HCl concentrations, and inappropriate use of bichromatic correction.
- Simple procedural and reagent modifications can enhance the accuracy of clinical laboratory DBIL determinations.