Performance Evaluation of Urine Osmolality Measurement on Sysmex UF-5000 and the Effect of Molecules and Particles in Urine.

BACKGROUND

Urine osmolality determines the concentration ability of the kidney. Therefore, it is used to assess the body's hydration status, electrolyte levels, and acid-base disturbances. We aimed to evaluate the analytical performance of osmolality measurement of the Sysmex UF-5000 (UF-5000), to examine the effect of different molecules and particles in the urine on the osmolality measurement.

METHODS

Complete urinalysis and conductivity-based osmolality analysis with UF-5000 and osmolality analysis with Advanced® Model 3320 Micro-Osmometer (AI-3320) by freezing point reduction method were performed in the urine samples. Samples were grouped as negative, glucosuria, proteinuria, hematuria, pyuria, crystalluria, and urobilinogen.

RESULTS

Total impressions were calculated as < 5% and accuracy values were < 1.66% in both analyzers. The regression equation was found to be y = -12.54 + 0.956x and the relative difference between the analyzers was 8.7% in 586 samples. When patients with Glucose > 2+ were excluded the regression equation of 507 samples was found as y = 5.10 + 0.948x and the relative difference was 4.6%. The percentages of samples with a difference greater than the allowable difference were 18.8%, 11.6%, 35.9%, 13.7%, 18.7%, and < 12.2% in all samples, all samples without glucosuria > 2+, glucosuria, glucosuria < 3+, proteinuria, and other subgroups, respectively.

CONCLUSIONS

Considering the good accessibility of the automated routine complete urine analyzer, UF-5000 can be considered to determine whether urine osmolality is within reference or should be measured by methods based on colligative properties. Thus, referral of patients to a clinic that uses the colligative measurement method may be used more effectively.