Saliva test could detect a host of diseases from type 2 diabetes to dementia

A simple saliva test for the compound that triggers gout attacks may help to detect other diseases.

A growing body of research suggests that measuring levels of uric acid in saliva may help diagnose more than a dozen conditions, from type 2 diabetes to dementia and cancer.

We produce up to two litres of saliva a day and while it’s 99 per cent water, it also contains more than 700 micro-organisms and compounds such as uric acid. This acid is created when the body processes purines, compounds normally produced by damaged or dead cells in the body, but which are also found in some food and drink, including liver, dried beans and beer.

Uric acid is removed from the body in urine. It is most commonly linked to gout — those affected have high levels of uric acid which forms crystals in the joints, usually the big toe, resulting in throbbing pain.

Uric acid builds up in the blood if there is too much purine in the diet, or if the body can’t get rid of it fast enough and is linked to many other diseases other than gout.

Now a new review of studies that had looked at the link between levels of uric acid in saliva and disease has concluded a saliva test for uric acid could be a non-invasive method for diagnosing serious illnesses that are associated with oxidative stress. This occurs when the body doesn’t produce enough antioxidants to deal with molecules, called free radicals, that damage tissues by a process called oxidation. Oxidative stress can contribute to a range of conditions, including type 2 diabetes.

As the review authors, from Datta Meghe University of Medical Sciences in India, explain in the journal Cureus, abnormally high levels of uric acid can be a marker of high blood pressure, cardiovascular disease, kidney disease, some cancers and metabolic syndrome (a group of health problems including obesity and high blood sugar, and a precursor to type 2 diabetes).

Previously a study in the journal Hypertension, published in 2018, found that women with the highest uric acid levels were twice as likely to develop high blood pressure, while men had a 37 per cent greater risk.

And a 2020 study in the Journal of Cancer found high levels of uric acid may be implicated in several cancers, including those of the digestive tract. Low concentrations have been associated with depression, anxiety, Parkinson’s and Alzheimer’s.

Professor Raj Persad, a consultant urologist at Bristol Urology, said: ‘We are continually looking for diagnostic markers such as uric acid that avoid invasive testing such as biopsy or blood testing.

‘Not only might we diagnose conditions but we might use them to pre-empt attacks, with speedier checks than waiting for standard lab tests.’

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