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Standardizing the A1C

By David Mendosa

Last Update: July 1, 2006

The Web site for the National Glycohemoglobin Standardization Program (NGSP) is technical. But the work that this program is doing is also highly relevant to anyone with diabetes.

Glycohemoglobin tests are better known to people with diabetes as hemoglobin A1c or HbA1c tests. Everybody with diabetes needs a to be tested two to four times a year—depending on how well controlled their diabetes is—according to the ADA's current Clinical Practice Recommendation.

The problem is…different types of assay methods.

The problem is that clinical laboratories have many different types of glycohemoglobin assay methods to chose from. And their results differ considerably. That's why the NGSP, sponsored in part by the ADA, began in 1996.

That much is clear, but I knew there was a lot more on the site than I could understand. That's why I interviewed David E. Goldstein, M.D., who chairs the NGSP Steering Committee. Dr. Goldstein is also a pediatric endocrinologist practicing in Columbia, Missouri, and professor of child health, internal medicine, and pathology at the University of Missouri.

When hemoglobin A1c tests first became available about 1978, there was only one assay method, and things were simple, Dr. Goldstein recalls. But as other methods became available, "by 1981 there was chaos."

It would have been even worse if they had known how important hemoglobin A1c tests were. But until about the time that the Diabetes Control and Complications Trial (DCCT) finished in 1993, no one knew the direct relationship between blood sugar and diabetic complications.

Still, "we became worried about it as new methods proliferated," Dr. Goldstein says. "We had an NIH conference in '82 or '83 about the state of things glycosalated and we issued a report that was in Diabetes Care in '84 that strongly recommended that the standardization of the test be accomplished, and we laid out some criteria for assay quality. And we thought it was done."

Hardly. It took the DCCT to give the scientific community the push it needed to standardize the test.

I told Dr. Goldstein that like most people with diabetes I knew that hemoglobin A1c tests still weren't standardized. But it seems that my knowledge was out of date.

"About 75 percent of all testing is now by methods that are certified as traceable to the DCCT," he replied. "Things are dramatically different than they were two years ago. So standardization is here. The biggest problem we are having is with colleagues in Europe who want to come up with a whole new number system."

How can you find out if the lab that does your hemoglobin A1c test use a standardized method? "The question that I would ask," Dr. Goldstein replies, "is 'are you using a DCCT certified assay method, a method that is certified as traceable to the DCCT reference as defined by the National Glycohemoglobin Standardization Program?'"

The laboratory that I use, Unilab in San Jose, gave the right answers. When I called, the medical director mentioned the correct acronyms DCCT and NGSP as well as the name of the assay used, Affinity HPLC, one of those on the List of NGSP Certified Methods.

Dr. Goldstein carefully explained the entire history of A1c standardization to me. Before I got through questioning him, he noted in passing that he got tired talking about it.

"We started working on this 1980," he says, "but it is worth it because the DCCT numbers are so important in terms of understanding outcome risks." We can all appreciate that he didn't get tired of working to get this crucial test standardized. 

The American Diabetes Association originally published this article on its Web site as one of my “About the Internet” columns.

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