title: Is this elderly patient dehydrated? Diagnostic accuracy of hydration assessment using physical signs, urine, and saliva markers.
abstract: OBJECTIVE
  Dehydration in older adults contributes to increased morbidity and mortality during hospitalization. As such, early diagnosis of dehydration may improve patient outcome and reduce the burden on healthcare. This prospective study investigated the diagnostic accuracy of routinely used physical signs, and noninvasive markers of hydration in urine and saliva.
  
  
  METHODS
  Prospective diagnostic accuracy study.
  
  
  METHODS
  Hospital acute medical care unit and emergency department.
  
  
  METHODS
  One hundred thirty older adults [59 males, 71 females, mean (standard deviation) age = 78 (9) years].
  
  
  METHODS
  Participants with any primary diagnosis underwent a hydration assessment within 30 minutes of admittance to hospital. Hydration assessment comprised 7 physical signs of dehydration [tachycardia (>100 bpm), low systolic blood pressure (<100 mm Hg), dry mucous membrane, dry axilla, poor skin turgor, sunken eyes, and long capillary refill time (>2 seconds)], urine color, urine specific gravity, saliva flow rate, and saliva osmolality. Plasma osmolality and the blood urea nitrogen to creatinine ratio were assessed as reference standards of hydration with 21% of participants classified with water-loss dehydration (plasma osmolality >295 mOsm/kg), 19% classified with water-and-solute-loss dehydration (blood urea nitrogen to creatinine ratio >20), and 60% classified as euhydrated.
  
  
  RESULTS
  All physical signs showed poor sensitivity (0%-44%) for detecting either form of dehydration, with only low systolic blood pressure demonstrating potential utility for aiding the diagnosis of water-and-solute-loss dehydration [diagnostic odds ratio (OR) = 14.7]. Neither urine color, urine specific gravity, nor saliva flow rate could discriminate hydration status (area under the receiver operating characteristic curve = 0.49-0.57, P > .05). In contrast, saliva osmolality demonstrated moderate diagnostic accuracy (area under the receiver operating characteristic curve = 0.76, P < .001) to distinguish both dehydration types (70% sensitivity, 68% specificity, OR = 5.0 (95% confidence interval 1.7-15.1) for water-loss dehydration, and 78% sensitivity, 72% specificity, OR = 8.9 (95% confidence interval 2.5-30.7) for water-and-solute-loss dehydration).
  
  
  CONCLUSIONS
  With the exception of low systolic blood pressure, which could aid in the specific diagnosis of water-and-solute-loss dehydration, physical signs and urine markers show little utility to determine if an elderly patient is dehydrated. Saliva osmolality demonstrated superior diagnostic accuracy compared with physical signs and urine markers, and may have utility for the assessment of both water-loss and water-and-solute-loss dehydration in older individuals. It is particularly noteworthy that saliva osmolality was able to detect water-and-solute-loss dehydration, for which a measurement of plasma osmolality would have no diagnostic utility.
authors.affiliation: School of Sport, Health and Exercise Sciences, College of Health and Behavioural Sciences, Bangor University, Bangor, United Kingdom. Electronic address: m.fortes@bangor.ac.uk.
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Fortes
authors.affiliation: School of Sport, Health and Exercise Sciences, College of Health and Behavioural Sciences, Bangor University, Bangor, United Kingdom.
authors.forename: Julian A
authors.initials: JA
authors.lastname: Owen
authors.affiliation: School of Sport, Health and Exercise Sciences, College of Health and Behavioural Sciences, Bangor University, Bangor, United Kingdom.
authors.forename: Philippa
authors.initials: P
authors.lastname: Raymond-Barker
authors.affiliation: Department of Geriatric Medicine, Gwynedd Hospital, Betsi Cadwaladr University Health Board, Bangor, United Kingdom.
authors.forename: Claire
authors.initials: C
authors.lastname: Bishop
authors.affiliation: Department of Geriatric Medicine, Gwynedd Hospital, Betsi Cadwaladr University Health Board, Bangor, United Kingdom.
authors.forename: Salah
authors.initials: S
authors.lastname: Elghenzai
authors.affiliation: School of Sport, Health and Exercise Sciences, College of Health and Behavioural Sciences, Bangor University, Bangor, United Kingdom.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Oliver
authors.affiliation: School of Sport, Health and Exercise Sciences, College of Health and Behavioural Sciences, Bangor University, Bangor, United Kingdom. Electronic address: n.walsh@bangor.ac.uk.
authors.forename: Neil P
authors.initials: NP
authors.lastname: Walsh
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis; D001806:Blood Urea Nitrogen; D003404:Creatinine / Q000652:urine; D003430:Cross-Sectional Studies; D003681:Dehydration / Q000175:diagnosis* / Q000628:therapy*; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D005440:Fluid Therapy / Q000379:methods; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D010808:Physical Examination / Q000379:methods*; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012015:Reference Standards; D018570:Risk Assessment; D012463:Saliva / Q000737:chemistry* / Q000378:metabolism; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D063189:Symptom Assessment / Q000379:methods; D006113:United Kingdom; D016482:Urinalysis; D014883:Water-Electrolyte Imbalance / Q000175:diagnosis
chemical_list: D015415:Biomarkers; D003404:Creatinine
keywords: Dehydration; clinical; diagnosis; hypovolemia; older; osmolality