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Evaluation of ames Multistix-SG for urine specific gravity versus refractometer specific gravity
American Journal of Clinical Pathology
|December 1, 1983
Summary
The Multistix-SG urine test strip showed poor accuracy for specific gravity compared to refractometry, misclassifying concentrated samples. This method is not cost-effective or clinically useful for assessing urine concentration.
Area of Science:
- Clinical Chemistry
- Urinalysis
- Diagnostic Testing
Background:
- Urine specific gravity is a key indicator of renal concentrating ability.
- Accurate measurement of urine specific gravity is essential for clinical diagnosis.
- Multiple reagent test strips offer convenience but require validation for accuracy.
Purpose of the Study:
- To compare the accuracy of urine specific gravity measurement using Multistix-SG reagent strips versus refractometry.
- To evaluate the clinical utility and cost-effectiveness of reagent strip-based specific gravity testing.
Main Methods:
- A comparative study involving 214 routine urine specimens.
- Urine specific gravity measured by Multistix-SG reagent strips and a TS Meter refractometer.
- Statistical analysis of agreement, bias, and misclassification rates.
Main Results:
- 72% agreement within +/- 0.005 between Multistix-SG and refractometer.
- Multistix-SG exhibited significant positive bias at pH <= 6.0 and negative bias at pH > 7.0.
- Up to 25% of concentrated urine specimens (SG >= 1.020) were misclassified by Multistix-SG.
Conclusions:
- Multistix-SG reagent strip specific gravity testing demonstrates significant bias and misclassification of concentrated urine.
- The performance limitations and additional cost make this method neither cost-effective nor clinically useful compared to refractometry.
- Refractometry remains the preferred method for accurate urine specific gravity determination.