Issue 91 Item 3 Afternoon Office Visits May Miss ½ of Diabetes Diagnosis

Doing a random blood glucose test in the afternoon can miss 50% of those with undiagnosed diabetes.

Application of current diabetes diagnostic criteria to patients seen during afternoon office visits may miss half of the patients who have undiagnosed diabetes, according to a report published in the December 27th issue of The Journal of the American Medical Association. This occurs as a result of the diurnal variation in fasting glucose, where levels are higher in the morning than in the afternoon. 

Dr. Maureen I. Harris, from the National Institute of Diabetes and Digestive and Kidney Diseases, in Bethesda, Maryland,  randomized 12,882 subjects, age 20 years or older, with no previously diagnosed diabetes to undergo a morning or afternoon fasting glucose evaluation.

Fasting plasma glucose levels from morning-examined subjects were significantly higher than levels from afternoon-examined subjects, the authors note. As a result, only half as many afternoon-examined subjects had glucose levels greater than 126 mg/dL compared with morning-examined subjects.

The fasting glucose level diagnostic of diabetes would have to be reduced to 114 mg/dL or greater in afternoon-examined patients, Dr. Harris’ team calculated, in order to achieve a prevalence comparable to that in morning-examined subjects when the standard level of 126 mg/dL or greater was employed. 

The researchers pointed out that many patients in the ambulatory care setting are seen in the afternoon, and these patients can be asked to fast for at least 4 hours before testing for diabetes.  Therefore regardless of the time of day that patients are tested, physicians need to confirm the diagnosis by repeat testing on a different day. 

Early morning rises in fasting glucose levels and insulin requirements (the ‘dawn phenomenon’) have been observed in patients with diabetes and in some, but not all, studies of nondiabetic persons. The data showing higher fasting levels of plasma glucose, serum insulin, and serum C peptide.  The Journal of the American Medical Association, Dec 27, 2001