CHICAGO Calling into question the accuracy of an afternoon blood sugar test for diabetes, researchers said the illness may be missed in some patients who have the test later in the day.

Based on a study of nearly 12,000 people, researchers found half as many patients met the criteria for diabetes based on their blood plasma glucose levels when tested in the afternoon versus the morning.

Diabetes causes a decline in insulin production that is needed to process food sugars and is marked by elevated levels of glucose in the blood and urine. If untreated, the disease can lead to blindness, heart disease and other serious ailments.

The study found elevated glucose levels indicating diabetes was reported in just 1.4 percent of afternoon test subjects compared to 2.8 percent of patients tested in the morning.

"Morning subjects had higher glucose values at every age compared with afternoon subjects," wrote study authors Rebecca Troisi, formerly of Social and Scientific Systems Inc. in Bethesda, Maryland, and Maureen Harris and Catherine Cowie from the National Institute of Diabetes and Digestive and Kidney Diseases.

The generally shorter fasting period prior to the afternoon tests may account for the lower blood sugar levels, and the researchers suggested lowering the threshold glucose level by at least 9.5 percent if testing is performed later in the day.

The study, which appeared in last week's Journal of the American Medical Association, found the median fasting time for those tested in the morning was 13.5 hours compared to 7 hours for subjects tested in the early or late afternoon.

"Regardless of the time of day that patients are tested, physicians need to confirm the diagnosis by repeat testing on a different day," the authors suggested. "For those initially tested in the afternoon, a confirmatory morning test may be advised."

(Reuter)