Estimated urinary osmolality based on combined urinalysis parameters: a critical evaluation

Matthijs Oyaert; Marijn M. Speeckaert; Joris R. Delanghe

doi:10.1515/cclm-2018-1307

Artikel

Estimated urinary osmolality based on combined urinalysis parameters: a critical evaluation

Matthijs Oyaert , Marijn M. Speeckaert und Joris R. Delanghe

Veröffentlicht/Copyright: 12. Februar 2019

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Aus der Zeitschrift Clinical Chemistry and Laboratory Medicine (CCLM) Band 57 Heft 8

Abstract

Background

Urinary conductivity allows a coarse prediction of urinary osmolality in most cases but is insensitive to the osmolal contribution of uncharged particles and the presence of roentgen contrast media. Urinary osmolality can be estimated on the recently introduced Sysmex UF-5000 urine analyzer using conductivity. In this study, we evaluated the analytical performance of this research parameter. Secondly, we aimed to improve the manufacturer’s algorithm for estimating urinary osmolality, based on standard urinalysis parameters (creatinine, glucose, relative density).

Methods

The analytical performance was determined and a prediction model to estimate urinary osmolality based on urinalysis parameters was developed. We further developed and validated a prediction model using another set of routine urine samples. In addition, the influence of roentgen contrast media on urinary osmolality was studied.

Results

The within-run and between imprecision for osmolality and conductivity measured on the Sysmex UF-5000 ranged from 1.1% to 4.9% and 0.7% to 4.8%, respectively. Multiple regression analysis revealed urinary creatinine, conductivity and relative density to be the strongest predictors to estimate urinary osmolality. A mean difference of 1.3 mOsm/kg between measured and predicted osmolality demonstrated that the predictive performance of our model was favorable. An excellent correlation between the relative density and % contrast media was demonstrated.

Conclusions

Urinary osmolality is an important parameter for assessing specimen dilution in urinalysis. Urinary conductivity, along with relative density and urinary creatinine allows a coarse prediction of urinary osmolality and is insensitive to the osmolal contribution of uncharged particles and the presence of roentgen contrast media.

Keywords: conductivity; contrast media; creatinine; glucose; relative density; urine osmolality

Corresponding author: Joris R. Delanghe, MD, PhD, Department of Clinical Chemistry, Ghent University, C. Heymanslaan 10, 9000 Ghent, Belgium; and Department of Laboratory Medicine, University Hospital Ghent, Ghent, Belgium, Phone: 09/332 29 56, Fax: 09/332 49 85

Acknowledgments

We would like to thank the laboratory technicians from the core laboratory of the University Hospital Ghent for their very valuable efforts.

Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: None declared.
Employment or leadership: None declared.
Honorarium: None declared.
Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.

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Received: 2018-12-07

Accepted: 2019-01-21

Published Online: 2019-02-12

Published in Print: 2019-07-26

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Artikel in diesem Heft

https://doi.org/10.1515/cclm-2018-1307

Schlagwörter für diesen Artikel

conductivity; contrast media; creatinine; glucose; relative density; urine osmolality