June 6, 2009 -- Diabetes experts on Friday urged a switch to a diagnostic test for the disease that's more useful to primary care doctors and more convenient for patients because it doesn't require fasting.
An international panel recommended that a test known as the hemoglobin A1c assay be the new standard test for diabetes. In the past, this test has primarily been used to monitor if diabetes treatment is working. However, the committee -- which unveiled its recommendations at this weekend's American Diabetes Association meeting in New Orleans, La. -- said the A1c test's long-term measurement of chronic blood sugar control problems provides a better diagnosis than current "snapshot" tests.
The test has not been adopted by all doctors for diagnostic purposes. Many of them prefer to rely first on the tried-and-true techniques such as the standard fasting plasma glucose test (FPG) and the less common oral glucose tolerance test -- tests that the A1c screening would unseat as the new standard.
Still, other physicians have welcomed the new screening. Dr. Joel Zonszein, director of the Clinical Diabetes Center at Montefiore Medical Center in New York, said many colleagues have been "waiting years for this to happen."
Proponents favor the A1c because it measures average blood glucose over the preceding two to three months, rather than just at one point in time, the researchers said.
"A1c values vary less than fasting plasma glucose values, and the assay for A1c has technical advantages compared with the glucose assay," said Dr. David M. Nathan of Massachusetts General Hospital, who chaired the expert committee.
"Also, testing for diabetes using A1c is more convenient and easier for patients who will no longer be required to perform a fasting or oral glucose tolerance test," Nathan added.
The recommendations -- made jointly by the American Diabetes Association, the International Diabetes Federation, and the European Association for the Study of Diabetes -- were published online today in Diabetes Care and will appear in the July issue of the journal.
Can Doctors Agree on A1c?
Many primary care doctors already use A1c screening as a first-line tool for diagnosis, while others use it in combination with FPG. One reason for caution about the A1c in the past, doctors said, has been concern about standardization in A1c screenings -- that is, whether doctors agree that a given result indicates that a patient has diabetes.
"It is my understanding that the A1c tests are now better standardized and, therefore, the A1c has been reconsidered as a screening tool," Dr. Gregory J. Anderson, a family practitioner at the Mayo Clinic in Rochester, Minn., wrote in an e-mail. "It makes more intuitive sense, as it reflects blood glucose levels over a much longer period of time. ... It is also more convenient for patients, as it does not need to be done fasting."
Currently, diabetes patients typically receive A1c screening twice a year to measure progress in controlling the disease. The question for physicians is how to determine whether they need diabetes care in the first place.
"Glucose impairment runs on a continuum, making selection of a specific value where diabetes risk begins somewhat arbitrary," Nathan said. "However, those persons whose A1c levels are close to the 6.5 percent diagnostic level are clearly at higher risk."
The committee also recommended screening all adult patients who are overweight and have other risk factors, such as family history of diabetes, high blood pressure or an abnormal blood lipid profile.
"What the test will do is to give the clinician and the patient a better integrated view of the average blood sugar," said Montefiore's Zonszein.
Dr. Christopher D. Saudek, a Johns Hopkins Hospital endocrinologist, agreed, adding that the main advantage of the A1c is that it "does not require fasting, so it can be done any time of day."
Also, he noted, because it measures glucose levels over months, rather than at the moment of a blood test, "it is less susceptible to patients 'tuning up' before they see a doctor [by] watching their diet for a day or two."
Not All Doctors Performing Test
Until now, some practitioners say, diabetes specialists have favored the more finely-tuned FPG and glucose tolerance measurements, while primary care doctors have been more willing to embrace the A1c.
To Dr. Thomas L. Schwenk, a professor of family medicine at the University of Michigan in Ann Arbor, this reflects different approaches to different patient populations. He said the A1c makes more sense in his practice.
"We are dealing with patients with many chronic problems and the obvious need for major lifestyle modifications, as well as managing six to eight medications directed at metabolic syndrome, not making decisions about tweaking insulin dosages by a couple units," he said.
Most agree that the A1c will reflect a more realistic pool of patients with diabetes and pre-diabetes.
It will help "chip away at the 40 percent of people with diabetes who don't know it," Saudek said.