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A comparison of creatinine vs. specific gravity to correct for urinary dilution of cotinine
Joshua E Muscat1, Anderson Liu, John P Richie
1Department of Public Health Sciences, Penn State College of Medicine, Hershey, PA, USA. jmuscat@psu.edu
Context:
The validity of urinary correction standards has not been established for most analytes.
Methods:
We compared urinary creatinine and specific gravity as dilution correction standards for cotinine in a community-based study of smokers.
Results:
Models of blood cotinine regressed against CR or SG (measured by total soluble solids) significantly improved the fit compared to a model without a dilution measure (P < 0.01). There were no differences in model fit between CR- and SG-corrected values. Both CR and SG were significant predictors of urinary cotinine regressed against cigarettes smoked per day (P < 0.01).
Conclusion:
CR and SG are valid and interchangeable correction standards.
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