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

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Diagnostic accuracy of calculated serum osmolarity to predict dehydration in older people: adding value to pathology lab reports. / Hooper, Lee; Abdelhamid, Asmaa; Ali, Adam; Bunn, Diane; Jennings, Amy; John, Garry; Kerry, Susan; Lindner, Gregor; Pfortmueller, Carmen; Sjöstrand, Fredrik; Walsh, Neil; Fairweather-Tait, Susan; Potter, John; Hunter, Paul; Shepstone, Lee.

In: BMJ Open, Vol. 5, No. 10, e008846, 21.10.2015.

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@article{01d1bafdadf245d286963a2cab09e4b1,
title = "Diagnostic accuracy of calculated serum osmolarity to predict dehydration in older people: adding value to pathology lab reports",
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), Sj{\"o}strand (emergency room) or Pfortmueller cohorts (hospitalised with liver cirrhosis). Reference standard for hydration status:Directly measured serum/plasma osmolality: current dehydration (serum osmolality >300mOsm/kg), impending/current dehydration (≥295mOsm/kg). Index tests:39 osmolarity equations calculated using serum indices from the same blood draw as directly measured osmolality. Results: Across five cohorts 595 older people were included, of whom 19{\%} were dehydrated (directly measured osmolality >300mOsm/kg). Of 39 osmolarity equations, five showed reasonable agreement with directly measured osmolality and three had good predictive accuracy in subgroups with diabetes and poor renal function. Two equations were characterized by narrower limits of agreement, low levels of differential bias and good diagnostic accuracy in ROC 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 295mOsm/L (sensitivity 85{\%}, specificity 59{\%}), to report dehydration risk opportunistically when serum glucose, urea and electrolytes are measured for other reasons in older adults.",
keywords = "dehydration, Older adults, Aged, osmolality, osmolarity, diagnostic accuracy, screening",
author = "Lee Hooper and Asmaa Abdelhamid and Adam Ali and Diane Bunn and Amy Jennings and Garry John and Susan Kerry and Gregor Lindner and Carmen Pfortmueller and Fredrik Sj{\"o}strand and Neil Walsh and Susan Fairweather-Tait and John Potter and Paul Hunter and Lee Shepstone",
year = "2015",
month = "10",
day = "21",
doi = "10.1136/bmjopen-2015-008846",
language = "English",
volume = "5",
journal = "BMJ Open",
issn = "2044-6055",
publisher = "British Medical Journal Publishing Group",
number = "10",

}

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TY - JOUR

T1 - Diagnostic accuracy of calculated serum osmolarity to predict dehydration in older people: adding value to pathology lab reports

AU - Hooper, Lee

AU - Abdelhamid, Asmaa

AU - Ali, Adam

AU - Bunn, Diane

AU - Jennings, Amy

AU - John, Garry

AU - Kerry, Susan

AU - Lindner, Gregor

AU - Pfortmueller, Carmen

AU - Sjöstrand, Fredrik

AU - Walsh, Neil

AU - Fairweather-Tait, Susan

AU - Potter, John

AU - Hunter, Paul

AU - Shepstone, Lee

PY - 2015/10/21

Y1 - 2015/10/21

N2 - 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 >300mOsm/kg), impending/current dehydration (≥295mOsm/kg). Index tests:39 osmolarity equations calculated using serum indices from the same blood draw as directly measured osmolality. Results: Across five cohorts 595 older people were included, of whom 19% were dehydrated (directly measured osmolality >300mOsm/kg). Of 39 osmolarity equations, five showed reasonable agreement with directly measured osmolality and three had good predictive accuracy in subgroups with diabetes and poor renal function. Two equations were characterized by narrower limits of agreement, low levels of differential bias and good diagnostic accuracy in ROC 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 295mOsm/L (sensitivity 85%, specificity 59%), to report dehydration risk opportunistically when serum glucose, urea and electrolytes are measured for other reasons in older adults.

AB - 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 >300mOsm/kg), impending/current dehydration (≥295mOsm/kg). Index tests:39 osmolarity equations calculated using serum indices from the same blood draw as directly measured osmolality. Results: Across five cohorts 595 older people were included, of whom 19% were dehydrated (directly measured osmolality >300mOsm/kg). Of 39 osmolarity equations, five showed reasonable agreement with directly measured osmolality and three had good predictive accuracy in subgroups with diabetes and poor renal function. Two equations were characterized by narrower limits of agreement, low levels of differential bias and good diagnostic accuracy in ROC 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 295mOsm/L (sensitivity 85%, specificity 59%), to report dehydration risk opportunistically when serum glucose, urea and electrolytes are measured for other reasons in older adults.

KW - dehydration

KW - Older adults

KW - Aged

KW - osmolality

KW - osmolarity

KW - diagnostic accuracy

KW - screening

U2 - 10.1136/bmjopen-2015-008846

DO - 10.1136/bmjopen-2015-008846

M3 - Article

VL - 5

JO - BMJ Open

JF - BMJ Open

SN - 2044-6055

IS - 10

M1 - e008846

ER -

ID: 60754220