Validity of a portable urine refractometer: The effects of sample freezing

摘要: Abstract The use of portable urine osmometers is widespread, but no studies have assessed the validity this measurement technique. Furthermore, it unclear what effect freezing has on osmolality. One-hundred participants mean (±SD) age 25.1 ± 7.6 years, height 1.77 ± 0.1 m and weight 77.1 ± 10.8 kg provided single samples that were analysed using freeze point depression (FPD) refractometry (RI). Samples then frozen at −80°C (n = 81) thawed prior to re-analysis. Differences between methods determined Wilcoxon's signed rank test. Relationships measurements intraclass correlation coefficients (ICC) typical error estimate (TE). Osmolality was lower (P = 0.001) RI (634.2 ± 339.8 mOsm · kgH2O−1) compared with FPD (656.7 ± 334.1 mOsm · kgH2O−1) TE trivial (0.17). Freezing significantly reduced osmolality (656.7 ± 341.1 606.5 ± 333.4 mOsm · kgH2O−1; P < 0.001), still highly re...