Routine blood testing for sodium, potassium, urea and glucose could be used to detect dehydration in older people, following new research that has found a “universal” approach to this form of screening.
Academics at the University of East Anglia, who led the research, have found the most accurate way of using results from these tests in an equation to screen for the condition.
After looking at a series of “osmolarity equations” currently being used to predict dehydration, they found one – developed by Khajuria and Krahn – showed the best results across all different groups of older people in the trial.
“Using routine blood tests in older people to screen for dehydration… would enable healthcare professionals to provide appropriate support in older people”
The study, published in the British Medical Journal, looked at 595 people over the age 65, including those who were healthy and lived independently, frail people living in residential care, and those in hospital.
The group also included men and women at a range of dehydration levels and spanned several European countries and took into account those with poor renal function and diabetes.
Those behind the research indicated this form of testing could in most cases replace the need for serum osmolality testing – a direct measurement taken in laboratories, which is costly and not available for widespread NHS screening of dehydration.
Lead researcher Lee Hooper from UEA’s Norwich Medical School, said: “A serum osmolality test measures the freezing point of blood serum to show how concentrated a sample of blood is. People’s blood becomes more concentrated as they become dehydrated.
“But it is an expensive and time consuming procedure – and clinical laboratories would not be able to handle routine screening,” she said.
Simpler tests such as urine measurements, which appear to work well in children and young adults, do not work in older adults, she noted.
“We wanted to find a universal equation which would be accurate for a broad range of elderly people including people with conditions such as diabetes”
“When our blood becomes more concentrated, as we become dehydrated, concentrations of serum sodium, potassium, urea and glucose rise. Many blood tests routinely measured in older people already check for all of these, and assess them independently,” added Ms Hooper.
She said a number of equations were already being used that included these blood test results but that they “vary considerably” and it wasn’t previously clear which ones worked for older people.
“We wanted to find a universal equation which would be accurate for a broad range of elderly people including people with conditions such as diabetes,” she said.
The research paper stated: “Using routine blood tests in older people to screen for dehydration using the Khajuria and Krahn formula for serum osmolarity would enable healthcare professionals and carers to provide appropriate support in older people by increasing fluid intake and improving and maintaining good hydration and thereby prevent associated poor health.
“This information could be provided automatically on the reports from pathology laboratories where serum sodium, potassium, urea and glucose have been measured, although to improve sensitivity (though increasing costs) positive results from this screening could be followed by assessment of directly measured serum osmolality,” it said.