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Analytical goal-setting for monitoring patients when two analytical methods are used
P H Petersen1, C G Fraser, J O Westgard
1Department of Clinical Chemistry, Odense University Hospital, Denmark.
Insights
Analytical errors in medical testing can impact patient care. This study presents a model to set allowable analytical imprecision and bias limits for serial testing methods, ensuring reliable patient monitoring.
Area of Science:
- Clinical chemistry
- Analytical toxicology
- Medical diagnostics
Background:
- Serial patient results often use multiple methods, requiring result transferability across time and location.
- Analytical errors (imprecision and bias) must be defined to ensure optimal patient care.
- Existing guidelines propose limits for analytical error based on biological variation.
Purpose of the Study:
- To develop a general model for relating analytical imprecisions of two methods and their bias to biological variation.
- To quantitatively determine goals for method imprecisions and allowable bias differences in clinical monitoring.
Main Methods:
- Utilized Harris's proposal relating desirable imprecision to within-subject biological variation.
- Developed a general formula incorporating analytical imprecisions and bias between two methods.
- Applied the derived formula to clinical monitoring scenarios with defined probability of change triggering clinical action.
Main Results:
- Established a quantitative relationship between analytical imprecisions, bias, and biological variation.
- Provided a framework for setting specific goals for method imprecision and bias in clinical monitoring.
- Demonstrated the application of the general model in clinical practice.
Conclusions:
- The developed model allows for quantitative determination of analytical performance goals for serial testing methods.
- Setting appropriate imprecision and bias limits is crucial for reliable patient monitoring and clinical decision-making.
- This approach facilitates the selection and validation of methods for longitudinal patient health assessment.
Abstract:
Serial results from an individual are often obtained using more than one method. Results should be transferable over time and locale. Every method has inherent analytical error, and goals are required to delineate the maximum allowable random (imprecision) and systematic (inaccuracy, bias) errors to facilitate optimal patient care. Based on Harris's proposal [Am J Clin Pathol 1979;72:374-82] that desirable imprecision should be less than or equal to one-half the within-subject biological variation, if the methods have negligible imprecision, then the maximum allowable bias between two methods used for monitoring is one-third of the within-subject biological variation. A more general model has been developed that relates the analytical imprecisions of two methods, and the bias between them, to biological variation. Applying the general formula derived in specific clinical monitoring situations in which a known change in serial results (occurring at a stated probability) stimulates clinical action allows goals for the imprecisions of the two methods and allows the difference in bias between them to be determined quantitatively.