Posted by Sten Westgard, MS
Clinical Laboratory News has a cover story on the new NACB LMPG guidelines on diabetes:
Diabetes Direction: NACB Guideline Update Captures Latest Evidence, Thought, Genna Rollins, Clinical Laboratory News, June 2011, Volume 37, No. 6.
The major new change is the addition of a diagnosis criterion for use with an HbA1c method. If an individual's HbA1c value exceeds 6.5% (or 48 mmol/mol), the NACB now recommends they be considered diabetic.
The implications of this national cutoff have not gone unnoticed. David Bruns, a member of the committee, noted,
"that the new diagnostic standard and improved HbA1c analytics makes it incumbent on labs to maintain the highest accuracy possible with HbA1c testing. 'If your method suddenly shifts so that your results go up by two-tenths of one percent, then anyone whose Hemoglobin A1c is 6.3 percent would have a reported result of 6.5 percent, and he or she would be diagnosed as a diabetic,' he observed. 'Applying that kind of error to the general population, there'd be millions of people incorrectly diagnosed if our assays went off by that amount. But people are not in the mode of getting worked up because they see their hemoglobin A1c quality control results go up by two-tenths of one percent. We need to change that.'"
At a level of 6.5%, a 0.2 shift is a bias of just 3%. Laboratories seeking to use the 6.5% cutoff will indeed need to carefully manage their method. Using an accuracy-based proficiency testing program will be very important. Here is where traceability and standardization make their impact felt in the laboratory. If labs want to use this new international cutoff for diabetes diagnosis, they have to be able to prove that they do not have a significant bias that renders the cutoff less useful.
Another important new recommendation in the NACB guideline: a tightened quality requirement for glucose meters. Back in 2010, the FDA held a conference about the poor performance found in glucose meters. The NACB guideline confirms this: a 20% quality requirement is too wide, 15% is more appropriate. (Take a look at which glucose meters can actually fulfill this performance requirement)
Again, the key quotation comes from Dr. Bruns:
"Bruns, who has been a leading advocate for more accurate BGMs, urged labs to stay on top of this issue. 'It’s a real problem, and not one clinicians had been aware of until recently. Now they’re more aware of it, but we need to continue to point out that there are real implications for people with diabetes that flow from errors in glucose meters,' he said. 'The FDA is acutely aware that meters have not been cleared for the kind of uses they’re being put to.'"
Those links again are:
Diabetes Direction: NACB Guideline Update Captures Latest Evidence, Thought, Genna Rollins, Clinical Laboratory News, June 2011, Volume 37, No. 6.
Comments