Lab Med Online.  2015 Oct;5(4):204-210. 10.3343/lmo.2015.5.4.204.

Evaluation of a Test Index Obtained by Coupling Protein with Specific Gravity of Screening Urine Test

• Hahn SH
• Park IK

• KMID: 2046382
• DOI: http://doi.org/10.3343/lmo.2015.5.4.204

Abstract

BACKGROUND
The 24-hr urine protein excretion test is regarded as a standard for quantitative urinary protein analysis; however, collection of urine over 24 hr is troublesome and errors may occur during the process. We obtained a test index reflecting diluted or concentrated urine by coupling the results of a simple and rapid routine urine analysis and evaluated its usefulness as a marker that quantitatively reflects the 24-hr urine protein excretion.
METHODS
The estimated urine protein-osmolality ratio (Pro/Osm) was obtained by two linear regression equations between urine dipstick protein and natural logarithm of the protein concentration, and between urine specific gravity (SG) and urine osmolality (Osm). Sensitivity and specificity of 'estimated urine Pro/Osm' and the widely used urine protein-creatinine ratio were evaluated for their efficiency in diagnosing pathological proteinuria and nephrotic proteinuria based on 24-hr urine protein excretion.
RESULTS
Moderate correlations were noted between protein concentration determined by the urine dipstick protein assay and natural logarithm of protein concentration (r=0.86) and between urine SG and urine Osm (r=0.74). The receiver operating characteristics analysis showed that an estimated urine Pro/Osm value of 0.045 had a sensitivity of 91.1% and a specificity of 88.6% for diagnosing pathological proteinuria, and a value of 0.204 had a sensitivity of 100% and a specificity of 80.4% for diagnosing nephrotic proteinuria.
CONCLUSIONS
Coupling the results of urine dipstick protein and urine SG determined by the routine analysis will provide additional useful information that will make the screening of renal diseases more cost-effective.

Keyword

Proteinuria; Routine urine analysis; Urine protein-osmolality ratio

MeSH Terms

Linear Models
Mass Screening*
Osmolar Concentration
Proteinuria
ROC Curve
Sensitivity and Specificity
Specific Gravity*

Figure

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  Fig. 1 Correlation between estimated urine Pro/Osm by the new equation and urine Pro/Cre. Abbreviations: Pro/Osm, protein/osmolality ratio; Pro/Cre, protein/creatinine ratio.

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  Fig. 2 ROC analysis of estimated urine Pro/Osm ratio by the new equation for diagnosis of pathological proteinuria (A) and nephrotic proteinuria (B). The values for area under the ROC curves for pathological proteinuria and nephrotic proteinuria were 0.954 (95% confidence interval, 0.917-0.991) and 0.912 (95% confidence interval, 0.852-0.971), respectively.

• 

  Fig. 3 ROC analysis of the quantitative urine protein/creatinine ratio for diagnosis of pathological proteinuria (A) and nephrotic proteinuria (B). The values for area under the ROC curves for pathological proteinuria and nephrotic proteinuria were 0.976 (95% confidence interval, 0.965-0.988) and 0.979 (95% confidence interval, 0.967-0.991), respectively.

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