Diagnostic accuracy of calculated serum osmolarity to predict dehydration in older people: adding value to pathology laboratory reports

Lee Hooper, Asmaa Abdelhamid, Adam Ali, Diane K Bunn, Amy Jennings, W Garry John, Susan Kerry, Gregor Lindner, Carmen A Pfortmueller, Fredrik Sjöstrand, Neil P Walsh, Susan J Fairweather-Tait, John F Potter, Paul R Hunter, Lee Shepstone, Lee Hooper, Asmaa Abdelhamid, Adam Ali, Diane K Bunn, Amy Jennings, W Garry John, Susan Kerry, Gregor Lindner, Carmen A Pfortmueller, Fredrik Sjöstrand, Neil P Walsh, Susan J Fairweather-Tait, John F Potter, Paul R Hunter, Lee Shepstone

Abstract

Objectives: To assess which osmolarity equation best predicts directly measured serum/plasma osmolality and whether its use could add value to routine blood test results through screening for dehydration in older people.

Design: Diagnostic accuracy study.

Participants: Older people (≥65 years) in 5 cohorts: Dietary Strategies for Healthy Ageing in Europe (NU-AGE, living in the community), Dehydration Recognition In our Elders (DRIE, living in residential care), Fortes (admitted to acute medical care), Sjöstrand (emergency room) or Pfortmueller cohorts (hospitalised with liver cirrhosis).

Reference standard for hydration status: Directly measured serum/plasma osmolality: current dehydration (serum osmolality>300 mOsm/kg), impending/current dehydration (≥295 mOsm/kg).

Index tests: 39 osmolarity equations calculated using serum indices from the same blood draw as directly measured osmolality.

Results: Across 5 cohorts 595 older people were included, of whom 19% were dehydrated (directly measured osmolality>300 mOsm/kg). Of 39 osmolarity equations, 5 showed reasonable agreement with directly measured osmolality and 3 had good predictive accuracy in subgroups with diabetes and poor renal function. Two equations were characterised by narrower limits of agreement, low levels of differential bias and good diagnostic accuracy in receiver operating characteristic plots (areas under the curve>0.8). The best equation was osmolarity=1.86×(Na++K+)+1.15×glucose+urea+14 (all measured in mmol/L). It appeared useful in people aged ≥65 years with and without diabetes, poor renal function, dehydration, in men and women, with a range of ages, health, cognitive and functional status.

Conclusions: Some commonly used osmolarity equations work poorly, and should not be used. Given costs and prevalence of dehydration in older people we suggest use of the best formula by pathology laboratories using a cutpoint of 295 mOsm/L (sensitivity 85%, specificity 59%), to report dehydration risk opportunistically when serum glucose, urea and electrolytes are measured for other reasons in older adults.

Trial registration numbers: DRIE: Research Register for Social Care, 122273; NU-AGE: ClinicalTrials.gov NCT01754012.

Keywords: GERIATRIC MEDICINE; NUTRITION & DIETETICS; PREVENTIVE MEDICINE.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Figures

Figure 1
Figure 1
Percentages of individuals whose calculated osmolarity fell within 2% of measured osmolality, by equation and by specific conditions*. DM: diabetes mellitus. *In assessing by alcohol intake we had limited information on recent alcohol intake in any cohort, but Dehydration Recognition In our Elders (DRIE) participants reported very low alcohol intake, and the Dietary Strategies for Healthy Ageing in Europe (NU-AGE) participants had usual alcohol intake assessments so we separated out those who drank ≥21 g alcohol/week (intake mean plus one SD). For Pfortmueller we separated out alcoholics, other cohorts were not represented.
Figure 2
Figure 2
ROC plots for each equation for each data set and for all data sets combined. DRIE, Dehydration Recognition In our Elders; NU-AGE, the Dietary Strategies for Healthy Ageing in Europe; ROC, receiver operating characteristic.
Figure 3
Figure 3
Suggested proforma for opportunistic assessment of hydration status by health laboratories.

References

    1. Siervo M, Bunn D, Prado C et al. . Accuracy of prediction equations for serum osmolarity in frail older people with and without diabetes. Am J Clin Nutr 2014;100:867–76. 10.3945/ajcn.114.086769
    1. El-Sharkawy AM, Sahota O, Maughan RJ et al. . Hydration in the older hospital patient—is it a problem? Age Ageing 2014;43:i33–5. 10.1093/ageing/afu046.1
    1. Stookey JD, Pieper CF, Cohen HJ. Is the prevalence of dehydration among community-dwelling older adults really low? Informing current debate over the fluid recommendation for adults aged 70+years. Public Health Nutr 2005;8:1275–85. 10.1079/PHN2005829
    1. Stookey JD. High prevalence of plasma hypertonicity among community-dwelling older adults: results from NHANES III. J Am Diet Assoc 2005;105:1231–9. 10.1016/j.jada.2005.05.003
    1. Bhalla A, Sankaralingam S, Dundas R et al. . Influence of raised plasma osmolality on clinical outcome after acute stroke. Stroke 2000;31:2043–8. 10.1161/01.STR.31.9.2043
    1. Stookey JD, Purser JL, Pieper CF et al. . Plasma hypertonicity: another marker of frailty? J Am Geriatr Soc 2004;52:1313–20. 10.1111/j.1532-5415.2004.52361.x
    1. Wachtel TJ, Tetu-Mouradjian LM, Goldman DL et al. . Hyperosmolarity and acidosis in diabetes mellitus: a three-year experience in Rhode Island. J Gen Intern Med 1991;6:495–502. 10.1007/BF02598216
    1. Deardorff DL. Osmotic strength, osmolality, and osmolarity. Am J Hosp Pharm 1980;37:504–9.
    1. Thomas DR, Cote TR, Lawhorne L et al. . Understanding clinical dehydration and its treatment. J Am Med Dir Assoc 2008;9:292–301. 10.1016/j.jamda.2008.03.006
    1. Naitoh M, Burrell LM. Thirst in elderly subjects. In: Vellas B, Albarede JL, Garry PJ, eds. Hydration and aging. Paris: Serdi, 1998:33–46.
    1. Hooper L, Bunn D, Jimoh FO et al. . Water-loss dehydration and aging. Mech Ageing Dev 2014;136–7:50–8. 10.1016/j.mad.2013.11.009
    1. Cheuvront SN, Kenefick RW, Charkoudian N et al. . Physiologic basis for understanding quantitative dehydration assessment. Am J Clin Nutr 2013;97:455–62. 10.3945/ajcn.112.044172
    1. American Medical Directors Association (AMDA). Dehydration and fluid maintenance in the long-term care setting. Columbia, MD, USA: American Medical Directors Association (AMDA), 2009.
    1. Perrier E, Vergne S, Klein A et al. . Hydration biomarkers in free-living adults with different levels of habitual fluid consumption. Br J Nutr 2013;109:1678–87. 10.1017/S0007114512003601
    1. Johnson EC, Muñoz CX, Le Bellego L et al. . Markers of the hydration process during fluid volume modification in women with habitual high or low daily fluid intakes. Eur J Appl Physiol 2015;115:1067–74. 10.1007/s00421-014-3088-2
    1. Hooper L, Abdelhamid A, Atreed NJ et al. . Clinical symptoms, signs and tests for identification of impending and current water-loss dehydration in older people. Cochrane Database Syst Rev 2015;4:CD009647 10.1002/14651858.CD009647.pub2
    1. Fortes MB, Raymond-Barker P, Bishop C et al. . Is this elderly patient dehydrated? Diagnostic accuracy of hydration assessment using physical signs, urine, and saliva markers. J Am Med Dir Assoc 2015;16:221–8. 10.1016/j.jamda.2014.09.012
    1. Vivanti A, Yu L, Palmer M et al. . Short-term body weight fluctuations in older well-hydrated hospitalised patients. J Hum Nutr Diet 2013;26:429–35. 10.1111/jhn.12034
    1. Cheuvront SN, Ely BR, Kenefick RW et al. . Biological variation and diagnostic accuracy of dehydration assessment markers. Am J Clin Nutr 2010;92:565–73. 10.3945/ajcn.2010.29490
    1. Thomas DR, Tariq SH, Makhdomm S et al. . Physician misdiagnosis of dehydration in older adults. J Am Med Dir Assoc 2003;4:251–4. 10.1097/01.JAM.0000083444.46985.16
    1. Kyle UG, Bosaeus I, De Lorenzo AD et al. . Bioelectrical impedance analysis—part I: review of principles and methods. Clin Nutr 2004;23:1226–43. 10.1016/j.clnu.2004.06.004
    1. Kafri MW, Myint PK, Doherty D et al. . The diagnostic accuracy of multi-frequency bioelectrical impedance analysis in diagnosing dehydration after stroke. Med Sci Monit 2013;19:548–70. 10.12659/MSM.883972
    1. Olde Rikkert MGM, van't Hof MA, Baadenhuysen H et al. . Individuality and responsiveness of biochemical indices of dehydration in hospitalized elderly patients. Age Ageing 1998;27:311–19. 10.1093/ageing/27.3.311
    1. Institute of Medicine. Panel on dietary reference intakes for electrolytes and water. Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. Washington DC, USA: National Academies Press, 2004.
    1. Cheuvront SN, Kenefick RW, Sollanek KJ et al. . Water-deficit equation: systematic analysis and improvement. Am J Clin Nutr 2013;97:79–85. 10.3945/ajcn.112.046839
    1. Wikipedia the free encyclopedia. Plasma osmolality. 2014. [cited 2015 Feb 19].
    1. MDcalc. Serum Osmolality/Osmolarity. 2015. [cited 2015 Mar 24]
    1. Longmore M, Wilkinson IB, Davidson EH et al. . Clinical Chemistry. In: Oxford handbook of clinical medicine. 8th edn Oxford: Oxford University Press, 2010:682.
    1. Joint British Diabetes Societies. The management of the hyperosmolar hyperglycaemic state (HHS) in adults with diabetes. 2012. JBDS 06
    1. Levey AS, Bosch JP, Lewis JB et al. . A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group. Ann Intern Med 1999;130:461–70. 10.7326/0003-4819-130-6-199903160-00002
    1. Berendson A, Santoro A, Pini A et al. . A parallel randomized trial on the effect of a healthful diet on inflammageing and its consequences in European elderly people: design of the NU-AGE dietary intervention study. Mech Ageing Dev 2013;134:523–30. 10.1016/j.mad.2013.10.002
    1. Santoro A, Pini A, Scurti M et al. . Combating inflammaging through a Mediterranean whole diet approach: the NU-AGE project's conceptual framework and design. Mech Ageing Dev 2014;136–137:3–13. 10.1016/j.mad.2013.12.001
    1. Hooper L, Bunn D. DRIE—Dehydration recognition in our elders. 2014.
    1. Sjöstrand F, Rodhe P, Berglund E et al. . The use of a noninvasive hemoglobin monitor for volume kinetic analysis in an emergency room setting. Anesth Analg 2013;116:337–42. 10.1213/ANE.0b013e318277dee3
    1. Pfortmueller CA, Wiemann C, Funk G-C et al. . Hypoglycemia is associated with increased mortality in patients with acute decompensated liver cirrhosis. J Crit Care 2014; 29:316.e7–12. 10.1016/j.jcrc.2013.11.002
    1. Fazekas AS, Funk G-C, Klobassa DS et al. . Evaluation of 36 formulas for calculating plasma osmolality. Intensive Care Med 2013;39:302–8. 10.1007/s00134-012-2691-0
    1. Zander R. Optimale Berechnung der Osmolalität. Physioklin, Mainz. 2012.
    1. Kopp JB. Osmolality study.Product literature for Wescor (Logan, UT) vapour pressure (‘‘dew point’‘) osmometer Model 5100. 1973.
    1. Gerich JE, Martin MM, Recant L. Clinical and metabolic characteristics of hyperosmolar nonketotic coma. Diabetes 1971;20:228–38. 10.2337/diab.20.4.228
    1. Hoffman RS, Smilkstein MJ, Howland MA et al. . Osmol gaps revisited: normal values and limitations. J Toxicol Clin Toxicol 1993;31:81–93. 10.3109/15563659309000375
    1. Koga Y, Purssell RA, Lynd LD. The irrationality of the present use of the osmole gap: applicable physical chemistry principles and recommendations to improve the validity of current practices. Toxicol Rev 2004;23:203–11. 10.2165/00139709-200423030-00006
    1. Centers for Disease Control and Prevention. National Health and Nutrition Examination Survey. 2015. [cited 2015 Feb 19]
    1. Cheuvront SN, Kenefick RW, Heavens KR et al. . A comparison of whole blood and plasma osmolality and osmolarity. J Clin Lab Anal 2014;28:368–73. 10.1002/jcla.21695
    1. Zweig MH, Campbell G. Receiver-operating characteristic (ROC) plots: a fundamental evaluation tool in clinical medicine. Clin Chem 1993;39:561–77.
    1. Bossuyt PM, Reitsma JB, Bruns DE et al. . Toward complete and accurate reporting of studies of diagnostic accuracy: the STARD initiative. Br Med J 2003;326:41–4. 10.1136/bmj.326.7379.41
    1. Bland JM, Altman DG. Measuring agreement in method comparison studies. Stat Methods Med Res 1999;8:135–60. 10.1191/096228099673819272
    1. Khajuria A, Krahn J. Osmolality revisited-deriving and validating the best formula for calculated osmolality. Clin Biochem 2005;38:514–19. 10.1016/j.clinbiochem.2005.03.001
    1. Seifarth CC, Miertschischk J, Hahn EG et al. . Measurement of serum and plasma osmolality in healthy young humans—influence of time and storage conditions. Clin Chem Lab Med 2004;42:927–32. 10.1515/CCLM.2004.150
    1. Bohnen N, Terwel D, Markerink M et al. . Pitfalls in the measurement of plasma osmolality pertinent to research in vasopressin and water metabolism. Clin Chem 1992;38:2278–80.
    1. Redetzki HM, Hughes JR, Redetzki JE. Differences between serum and plasma osmolalities and their relationship to lactic acid values. Exp Biol Med 1972;139:315–18. 10.3181/00379727-139-36133
    1. Burnett RW, Covington AK, Fogh-Andersen N et al. . Use of ion-selective electrodes for blood-electrolyte analysis. Recommendations for Nomenclature, Definitions and Conventions. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Scientific Division Working Group on Selective Electrodes. Clin Chem Lab Med 2000;38:363–70. 10.1515/CCLM.2000.052
    1. Dimeski G, Morgan TJ, Presneill JJ et al. . Disagreement between ion selective electrode direct and indirect sodium measurements: estimation of the problem in a tertiary referral hospital. J Crit Care 2012;27:326.e9–16. 10.1016/j.jcrc.2011.11.003
    1. Edelman IS, Leibman J, O'Meara MP et al. . Interrelations between serum sodium concentration, serum osmolarity, and total exchangeable sodium, total exchangeable potassium, and total body water. J Clin Invest 1958;37:1236–56. 10.1172/JCI103712
    1. Heavens KR, Kenefick RW, Caruso EM et al. . Validation of equations used to predict plasma osmolality in a healthy adult cohort. Am J Clin Nutr 2014;100:1252–6. 10.3945/ajcn.114.091009

Source: PubMed

Sponsorer och medarbetare

Medicinska tillstånd

Läkemedelsinterventioner

3
Prenumerera