Afternoon tests 'could miss diabetes'

Test resulted could be skewed if there is too little fasting

Carrying out blood glucose tests to diagnose diabetes in the afternoon could mean cases are overlooked, say experts.

The formula for working out who is diabetic and who is not is based on a lengthy period prior to the test in which the patient is not allowed to eat.

However, a study in the Journal of the American Medical Association suggests that many patients undergoing tests in the afternoon have not been fasting as long as those tested in the morning.

The latter group have often not eaten anything since the previous day.

It is estimated that there are many thousands of diabetics in the UK who do not know they have developed the illness.

Higher risk

This places them at greater risk of complications such as eye disease and high blood pressure, which can contribute to heart disease.

If they suffer some of the more common symptoms, such as excessive fatigue or urination, a GP can carry out a number of tests to confirm or disprove the presence of diabetes.

One of the most common is to measure the level of glucose in the blood after the patient has been fasting for some time.

Researchers from the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland, US, looked at almost 13,000 patients, split evenly between those tested in the morning and afternoon.

The average fasting time for those tested in the morning, was 13.5 hours, whereas those tested in the afternoon had fasted on average for only seven hours.

Correspondingly, blood glucose levels were found to be higher among those tested in the morning, meaning that more borderline diabetics were detected.

Repeat needed

The authors suggested: "Regardless of the time of day that patients are tested, physicians need to confirm the diagnosis by repeat testing on a different day.

"For those initially tested in the afternoon, a confirmatory morning test may be advised."

A spokesman for Diabetes UK said that, as most testing was carried out by GPs in their surgeries, it was not always possible to guarantee a morning appointment appointment.

She said a fast of at least 10 hours prior to testing was desireable.

"This is interesting research and we'll certainly be looking at it further," she added.