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Intraperson variability. Magnitude, source, and influence on interpretation and diagnosis
Annals of Clinical Biochemistry
|January 1, 1978
Summary
Understanding within-person variation (VarWP) is crucial for accurate clinical chemistry diagnostics. Reducing VarWP through improved analytical methods or standardized procedures enhances diagnostic reliability, particularly for conditions like hypokalemia.
Area of Science:
- Clinical Chemistry
- Biostatistics
- Medical Diagnostics
Background:
- In steady-state individuals, repeated test results exhibit fluctuations around a central value (setting).
- Clinical practice often relies on a single test value as an estimate of this setting, introducing potential approximation errors.
Purpose of the Study:
- To discuss the diagnostic consequences of using single test values versus accounting for within-person variation (VarWP).
- To illustrate these consequences using common clinical chemistry measurements and the detection of hypokalemia.
Main Methods:
- Discussion of the impact of within-person variation (VarWP) on diagnostic accuracy.
- Analysis of how VarWP magnitude influences the consequences of approximation.
- Consideration of strategies to reduce VarWP, including analytical improvements, replicate analysis, and standardized procedures.
Main Results:
- The magnitude of diagnostic consequences is directly proportional to the proportion of total variation attributable to VarWP.
- High VarWP necessitates strategies to reduce it, such as improved analytical techniques or standardized venepuncture.
Conclusions:
- Reducing VarWP is essential when it constitutes a high proportion of total variation to improve diagnostic reliability.
- Specific interventions depend on the source of VarWP, whether analytical error or biological fluctuation.