Warning over use of standard but ‘ineffective’ hydration tests

Nurses and other staff working in care settings often use simple tests to see if an older person is dehydrated, including looking at their eyes, skin or asking if they feel thirsty.

“We found that none of them were able to accurately identify people with dehydration”

Diane Burn

But research by the University of East Anglia (UEA) – published in the Journal of the American Medical Directors Association – suggests these methods “lack even the most basic levels of diagnostic accuracy” and could cause harm.

Low-intake dehydration – when people do not drink enough fluids to stay healthy – is common in older people for a variety of reasons including not remembering to drink, difficulty accessing or lifting drinks, and because the sensation of feeling thirsty diminishes with age.

The researchers noted that standard tests for dehydration – currently used in care homes across the country – included looking at the eyes, skin, inside the mouth or feeling under the arm to check for dryness.

Staff may also check to see if there has been a drop in blood pressure or ask if someone feels thirsty, headachy or tired, they said.

“These tests have long been described as standard clinical indicators of dehydration and their use is advocated in nursing and medical text books, care guidelines and many health-related websites,” said lead researcher Lee Hooper from UEA’s medical school.

“But we wanted to see if these tests work in older people living in care homes, how accurate they are and whether they really tell us if someone is dehydrated,” he noted.

“This is important to know because using a test, which doesn’t work is telling us the wrong thing and health professionals may provide the wrong care as a result,” she added.

In all, 188 men and women living in care homes in Norfolk and Suffolk took part in the study, which was funded by the National Institute for Health Research.

Participants underwent a number of different standard tests including looking at their mouth and feeling under their arm, having their blood pressure, pulse and temperature measured and answering questions about how they were feeling, including whether they felt thirsty or not.

They were also given a blood test to test for serum osmolality, described as the “gold standard” test for measuring low-intake dehydration.

“We really need an inexpensive, easy-to-do test for dehydration in older people”

Diane Burn

The blood tests showed 20% of residents were dehydrated with another 28% on the verge of dehydration but the researchers found none of the commonly-used signs and symptoms usefully discriminated between those with or without low-intake dehydration at either point.

“This study consolidates evidence that commonly-used signs and symptoms lack even basic levels of diagnostic accuracy,” said the paper.

Reliance on the basic tests “could cause harm to older adults” resulting in people being exposed to “unnecessary interventions” if the tests wrongly shows they are dehydrated when they are not, said the document.

Meanwhile, false tests results may “discourage staff from providing the older person with the required increased fluids” when that person is dehydrated.

Lead author Dr Diane Burn from UEA’s School of Health Sciences said the findings indicated nurses and others should stop using the basic tests.

“When we analysed the results of all the simple tests, we found that none of them were able to accurately identify people with dehydration and we recommend they be withdrawn from practice,” she said.

However, the paper suggests “there is a reluctance to discontinue current ineffective methods of assessment”.

Dr Burn said there was a clear need for a new type of test for dehydration in the elderly.

“While blood tests are the most accurate way of telling if someone is dehydrated, this is expensive and not easily done in care homes unless a doctor orders the test,” she said.

“We really need an inexpensive, easy-to-do test for dehydration in older people, and once which works,” she added.