Urine reagent strips are inaccurate for assessing hypohydration: A brief report
Adams JD, Captain-Jimenez C, Huggins RA, Casa DJ, Mauromoustakos A, and Kavouras SA. Clin J Sport Med. [Epub Ahead of Print]. 2018.
Take Home Message: Reagent strips are not very accurate at detecting a person with hypohydration.
Assessing athlete hydration is an important part of ensuring athlete safety, especially in weight-dependent sports such as wrestling. While refractometry is the gold standard, reagent strips are also commonly available as an alternative. To date, no one has directly compared the diagnostic ability of reagent strips to diagnose hypohydration compared to refractometry. Therefore, Adams and colleagues completed a study to investigate the validity of reagent strips to diagnose hypohydration. A total of 414 urine samples from healthy adults and high school football players were obtained as part of a larger study and analyzed using both reagent strips and refractometry. All testing was performed within 2 hours of urination. Hypohydration cutoff was defined at 2 different levels (>1.020 and >1.025) both of which are used by state high school organizations. Overall, reagent strips showed low to moderate accuracy and had a high false positive rate. Further, positive and negative likelihood ratios for the >1.020 and >1.025 cutoff points were 1.2 and 1.1, and 0.83 and 0.77, respectively.
Overall, the current study demonstrated that compared to the gold standard of refractometry, reagent strips were not accurate enough in identifying hypohydration. This result supports a recent decision by the NCAA to no longer allow reagent strips in wrestling weight certification due to inaccuracies. Clinicians who work with weight-dependent athletes, such as wrestlers, should use refractometry to accurately and quickly assess an athlete’s hydration status. It is possible, however, that more research regarding the accuracy of reagent strips in the future could yield better results as technology improves. Until this time though refractometry should remain as the primary method of assessing hydration.
Questions for Discussion: Have you used reagent strips in your current clinical practice? What factors attributed to your use of reagent strips and would you consider using only refractometry after reading the current study?