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Calibration as a source of imprecision in cholesterol testing. Ramifications for patient risk classification
H D Epstein1, H C Nipper, G L Horowitz
1Department of Pathology, Charles A. Dana Research Institute, Boston, Mass.
Archives of Pathology & Laboratory Medicine
|April 1, 1990
Summary
Routine recalibration of cholesterol assay systems can reduce precision and alter patient risk classification. Frequent factor recalculation, compared to fixed factors, led to less precise cholesterol measurements and different patient risk assessments.
Area of Science:
- Clinical Chemistry
- Laboratory Medicine
- Diagnostic Assays
Background:
- Cholesterol assay systems require calibration for accurate results.
- Routine recalibration practices may impact assay precision and reliability.
Purpose of the Study:
- To compare the precision and impact on patient risk classification of a fixed calibration factor versus a recalculated factor for an enzymatic cholesterol assay.
- To evaluate the effect of routine recalibration on cholesterol measurement accuracy.
Main Methods:
- An enzymatic cholesterol assay on a centrifugal analyzer was used.
- Two data reduction methods were compared: a fixed calibration factor and a factor recalculated per run.
- Precision was assessed using quality control materials over 36 batch runs.
- Patient serum specimens were classified based on risk levels using both methods.
Main Results:
- No statistically significant difference in mean cholesterol values was found between the fixed and recalculated factor methods.
- The fixed factor method demonstrated significantly greater precision in all tested conditions.
- A significant proportion of patient results (9.4%) led to different risk classifications based solely on the data reduction method used.
Conclusions:
- Routine recalibration of this cholesterol assay system decreased precision rather than improving it.
- Recalibration practices can introduce discrepancies in patient cholesterol risk classification.
- Fixed calibration factors may offer superior precision and consistent patient risk assessment compared to routine recalibration.