medigraphic.com
Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán

2018, Number 6

<< Back

Rev Invest Clin 2018; 70 (6)

Calculated Versus Measured Urine Osmolarity: Accuracy of Estimated Urine Density

Vidal-Mayo JJ, Olivas-Martínez A, Pérez-Díaz I, López-Navarro JM, Sánchez-Landa E, Carrillo-Maravilla E, Portillo-González M, Fagundo-Sierra R, de Jesús Leal-Villareal MA

Language: English
References: 19
Page: 310-318
PDF size: 285.84 Kb.


ABSTRACT

Background: Urine osmolarity (OsmU) is the gold standard for the evaluation of the kidney’s urine concentration capacity; nevertheless, urinary density (UD) is often used as a surrogate for its estimation. Objective: The objective of this study was to analyze the accuracy of UD in estimating OsmU. Materials and Methods: A transversal study including patients with simultaneous determination of UD measured with refractometry and OsmU measured by osmometer (OsmUm). We multiplied the last two digits of the UD by 35, 30, 32, 33.5, and 40 to estimate OsmU; the estimates were considered precise if the value was ± 30 mOsm/kg from the OsmUm. A Bland–Altman analysis was conducted. Results: Among 205 patients, there was no difference between OsmUm and the estimated form when using a factor of 33.5 (p = 0.578). When analyzing by the absence or presence of proteinuria and/or glycosuria, there were no differences when using the factors 35 (p = 0.844) and 32 with adjusted UD (p = 0.898). In the linear correlation analysis, values for Pearson’s r = 0.788 and r2 = 0.621 were obtained (p ‹ 0.001). The areas under the curve obtained by the receiver operating characteristics curves to estimate urine osmolarity values ‹ 100 and › 600 mOsm/kg were › 0.90. Conclusion: The estimation of the OsmU from UD showed adequate perf rmance. If an osmometer is unavailable, we recommend using the factor 35 for clean samples and 32 with adjusted UD for samples with proteinuria and/or glycosuria.


REFERENCES

  1. Chadha V, Garg U, Alon US. Measurement of urinary concentration: a critical appraisal of methodologies. Pediatr Nephrol. 2001;16:374-82.

  2. Rose BD, Post TW, editors. Clinical Physiology of Acid Base and Electrolyte Disorders. 5th ed. New York: Mc Graw Hill; 2001.

  3. Elias-Costa C, Bettendorff MC, Bupo S, Ayuso S, Vallejo G. Medición comparativa de la densidad urinaria: tira reactiva, refractómetro y densitómetro. Arch Argent Pediatr. 2010;108:234-8.

  4. List AF, Hainsworh JD, Davis BW, Hande KR, Greco FA, Johnson DH. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in small-cell lung cancer. J Clin Oncol. 1986;4:1191-8.

  5. Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrol Dial Transplant. 2014;29 Suppl 2:11-139.

  6. Hoorn EJ, Halperin ML, Zietse R. Diagnostic approach to a patient with hiponatremia: traditional versus physiology based options. QMJ. 2005;98:529-40.

  7. Perrier ET, Bottin JH, Vecchio M, Lemetais G. Criterion values for urine-specific gravity and urine color representing adequate water intake in healthy adults. Eur J Clin Nutr. 2017;71:561-3.

  8. Yeh HC, Lin YS, Kuo CC, et al. Urine osmolality in the US population: implications for environmental biomonitoring. Environ Res. 2015;136:482-90.

  9. Voinescu G, Shoemaker M, Moore H, Khanna R, Nolph KD. The relationship between osmolality and specific gravity. Am J Med Sci. 2002;323:39-42.

  10. Souza AC, Zatz R, de Oliveira RB, et al. Is urinary density an adequate predictor of urinary osmolality? BMC Nephrol. 2015;16:46.

  11. Miller BE, Paton A, de Wardener HE. Maximum urine concentration. Br Med J. 1954;2:901-5.

  12. Miller RB. Urinalysis. In: Massry SG, Glassock RJ, editors. Textbook of Nephrology. Baltimore: Williams and Wilkins; 1983. p. 11.3-24.

  13. Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group. KDIGO clinical practice guideline for acute kidney injury. Kidney Inter. 2012;2:1-138.

  14. Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Inter Suppl. 2013;3:1-150.

  15. Bakhshandeh S, Morita Y. Comparison of urinary concentration tests: osmolality, specific gravity, and refractive index. Mich Med. 1975;74:399-403.

  16. Dorizzi R, Pradella M, Bertoldo S, Rigolin F. Refractometry, test strip, and osmometry compared as measures of relative density of urine. Clin Chem. 1987;33:190.

  17. Medler S, Harrington F. Measuring dynamic kidney function in an undergraduate physiology laboratory. Adv Physiol Educ. 2013;37:384-91.

  18. Imran S, Eva G, Christopher S, Flynn E, Henner D. Is specific gravity a good estimate of urine osmolality? J Clin Lab Anal. 2010; 24:426-30.

  19. Lamas C, De Pozo C, Villabona C. Guía clínica de manejo de la diabetes insípida y del síndrome de secreción inapropiada de hormona antidiurética en el postoperatorio de la cirugía hipofisaria. Endocrinol Nutr. 2014;61:e12-5.




2020     |     www.medigraphic.com