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A comparison of dilution adjustment methods for urinary enzymes
A J Verplanke1, R F Herber, J P Broersen
1Coronel Laboratory for Occupational and Environmental Health, University of Amsterdam, Netherlands.
The Science of the Total Environment
|June 9, 1992
Summary
Urinary dilution adjustment methods, using creatinine, can reduce variability in enzyme measurements. Optimal adjustments were found for alanine amino peptidase and beta-galactosidase, but not NAG, suggesting potential for personalized enzyme reference intervals.
Area of Science:
- Biochemistry
- Clinical Chemistry
- Urology
Background:
- Urinary flow variability significantly impacts intra-individual concentrations of urinary substances.
- Accurate measurement of urinary enzymes requires accounting for urine dilution.
Purpose of the Study:
- To compare linear and non-linear urinary dilution adjustment methods for three key urinary enzymes.
- To determine the optimal dilution adjustment for alanine amino peptidase (AAP), beta-galactosidase (beta GAL), and N-acetyl-beta, D-glucosaminidase (NAG).
Main Methods:
- Evaluated linear and non-linear adjustments using urinary flow, creatinine (CREAT), and urinary density (UD).
- Assessed adjustment efficacy for AAP, beta GAL, and NAG concentrations in urine samples.
Main Results:
- Optimal non-linear adjustment for AAP: AAPadjusted = AAPmeasured/(CREATmeasured)^0.824.
- Optimal non-linear adjustment for beta GAL: beta GALadjusted = beta GALmeasured/(CREATmeasured)^0.878.
- Conventional linear adjustment with specific gravity (SG) was optimal for NAG.
Conclusions:
- Specific non-linear creatinine-based adjustments effectively reduce variability for AAP and beta GAL.
- The utility of these methods for population-based enzyme reference intervals remains undetermined.
- Dilution adjustments may prove valuable for establishing personalized reference intervals by reducing intra-individual variability.