Document Type

Article

Publication Date

12-2003

Department 1

Health Sciences

Abstract

Objective: To investigate the reliability and validity of refractometry, hydrometry, and reagent strips in assessing urine specific gravity in collegiate wrestlers.

Design and Setting: We assessed the reliability of refractometry, hydrometry, and reagent strips between 2 trials and among 4 testers. The validity of hydrometry and reagent strips was assessed by comparison with refractometry, the criterion measure for urine specific gravity.

Subjects: Twenty-one National Collegiate Athletic Association Division III collegiate wrestlers provided fresh urine samples.

Measurements: Four testers measured the specific gravity of each urine sample 6 times: twice by refractometry, twice by hydrometry, and twice by reagent strips.

Results: Refractometer measurements were consistent between trials (R 5 .998) and among testers; hydrometer measurements were consistent between trials (R 5 .987) but not among testers; and reagent-strip measurements were not consistent between trials or among testers. Hydrometer (1.018 6 0.006) and reagent-strip (1.017 6 0.007) measurements were significantly higher than refractometer (1.015 6 0.006) measurements. Intraclass correlation coefficients were moderate between refractometry and hydrometry (R 5 .869) and low between refractometry and reagent strips (R 5 .573). The hydrometer produced 28% false positives and 2% false negatives, and reagent strips produced 15% false positives and 9% false negatives.

Conclusions: Only the refractometer should be used to determine urine specific gravity in collegiate wrestlers during the weight-certification process.

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