Many elderly patients end up suffering from dehydration due to not drinking enough fluid, and doctors, nurses and carers all know to keep checking up on the hydration levels of their patients. However, the methods they use to do this may be flawed, according to researchers from the University of East Anglia (UEA).
Currently, the standard method of checking for dehydration is to administer a urine test. If a patient's urine sample is too dark or the urine specific gravity is too high, it is usually taken to mean that they are dehydrated. However, Dr Lee Hooper - lead researcher at UEA's Norwich Medical School - decided to test this theory.
He and his team tested both the blood and urine of 383 men and women aged over 65, all of whom were living in residential care, nursing homes, or in their own homes in Norfolk and Suffolk.
The researchers measured the serum osmolality of the participant's blood, to see if they were drinking enough fluids to stay hydrated. The urine samples were tested for colour, cloudiness, specific gravity, osmolality, volume, glucose, and pH. The results showed that the urine tests had a very low diagnostic accuracy.
Dr Hooper said: "Assessing a urine sample is simple and cheap. But our research shows that urine tests for dehydration are not fit for purpose - either alone or as part of a wider tranche of tests. They are not sensitive or specific enough.
"Urine tests will indicate that some people are dehydrated when they are not, but the urine tests also miss some older adults who really are dehydrated."
The issue with this test on elderly patients is that it depends a lot on healthy kidney function. However, as people age their kidneys tend not to work as well as they used to, which can make a urine test inaccurate.
In addition, there are many other factors that can affect the qualities of a patient's urine beyond dehydration. For example, certain medical conditions, medications such as warfarin and certain foods such as beetroot or blackberries can all affect urine's colour.
"There is a great need to develop simple, inexpensive and non-invasive tools for the assessment of dehydration in older people," said Dr Hooper.
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