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The exponentially weighted moving average (EWMA) rule compared with traditionally used quality control rules
1Department of Forensic Chemistry, University of Copenhagen, Copenhagen, Denmark. linnet@post7.tele.dk
Clinical Chemistry and Laboratory Medicine
|April 8, 2006
Summary
The exponentially weighted moving average (EWMA) rule demonstrates superior performance in detecting systematic errors in clinical chemistry quality control compared to traditional methods. This makes EWMA a valuable tool for enhancing laboratory accuracy and reliability.
Area of Science:
- Clinical Chemistry
- Quality Control
- Statistical Process Control
Background:
- The exponentially weighted moving average (EWMA) rule is a recognized industrial quality control method.
- Its application and effectiveness in clinical chemistry require further evaluation.
Purpose of the Study:
- To assess the power of the EWMA rule for internal quality control in clinical chemistry.
- To compare its performance against commonly used control rules.
Main Methods:
- Simulations were employed to compare the EWMA rule with standard clinical chemistry control rules.
- Type I error levels were standardized for unbiased comparison.
Main Results:
- The EWMA rule outperformed simple and multi-rules for systematic errors up to 2-3 standard deviations.
- For a 2s systematic error, EWMA showed 0.30 power versus 0.15 for the 1(3s) rule.
- EWMA was superior to multi-rules across all tested error levels, e.g., detecting 1s systematic error with 0.4 power compared to 0.2.
Conclusions:
- The EWMA rule is an effective control strategy for systematic errors in clinical chemistry.
- It warrants consideration for widespread adoption in laboratory quality control.