Dehydration is a common problem among older people and could, in future, be diagnosed more easily using a simple blood test. This requires putting the results of routine tests into a mathematical equation. The study was published in “BMJ Open”.
Researchers from the University of East Anglia (Norwich) looked for an alternative to the time-consuming and expensive osmolarity test, currently the best method to determine dehydration. When someone has not had enough to drink, the blood becomes more concentrated and the levels of sodium, potassium, urea and glucose rise.
There are a number of mathematical equations that link these four variables. But it was unclear which one is most useful for elderly people. The researchers tested the accuracy of 39 different equations in 595 people over the age of 65. Participants included healthy people who lived independently, frail people living in residential care, people in hospital care and people with poor kidney function as well as diabetes.
The osmolarity equation by Khajuria and Krahn demonstrated the greatest accuracy for all participants, regardless of sex and health status. “We propose that clinical laboratories use this equation to report on the hydration status of older people when reporting blood test results that include sodium, potassium, urea and glucose. We hope our findings will lead to pragmatic screening in older people to allow early identification of dehydration. This would help doctors nurses and carers support older people to increase their fluid intake,” said study author Lee Hooper.