Agreement and Reliability Between Urine Reagent Strips and Refractometry for Field Assessment of Hydration in Ultra-Trail Runners.

Both Pearson ( r = 0.92 to 0.99) and Spearman rank ( r s = 0.91 to 0.98) correlation coefficients were nearly identical and highly significant (all p < 0.01), indicating excellent agreement between methods and demonstrating that the ordinal nature of strip data did not affect the strength of the relationship.

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