Urine colour, void number detect underhydration in adults, children

A recent study suggests the utilization of urine colour alone and the combination of urine colour (UC) with void number as a simple field-measure to identify underhydration in adults and children based on elevated urine osmolality (UOsm).

The authors tested the diagnostic ability of two combined practical markers for elevated UOsm (underhydration) in free-living adults (n=101, mean age 40±14 years, 52 female, 1.70±0.95 m, 76.7±17.4 kg, 26.5±5.5 kg/m²) and children (n=210, 105 female, 1.49±0.13 m, 43.4±12.6 kg, 19.2±3.2 kg m^-2), who collected their urine within 24 hours.

Urine was examined for UOsm and UC; the number of voids (void) was also recorded. The authors then carried out receiver operating characteristic (ROC) analysis for UC, void, and combination of UC and void to determine the markers’ diagnostic ability for detecting underhydration based on elevated UOsm (≥800 mmol kg⁻¹).

In linear regression analysis, UC significantly correlated with UOsm in both adults (R², 0.38; p<0.001) and children (R², 0.45; p<0.001). Void also showed a significant association with UOsm in both adults (R², 0.13; p<0.001) and children (R², 0.15; p<0.001).

In adults, the combination of UC >3 and void <7 resulted in an overall diagnostic ability for underhydration of 97 percent, with sensitivity of 100 percent and specificity of 88 percent. In children, when UC >3 and void <5 were combined, the overall diagnostic ability for underhydration was 89 percent, with sensitivity and specificity of 100 percent and 62 percent, respectively.