During a Current Issues session jointly sponsored by the ADA and the American Association for Clinical Chemistry , two experts debated whether point-of-care (POC) A1C should be used to diagnose diabetes.
Debate—Joint ADA/AACC Presentation—Point-of-Care HbA1c—Should We Use it to Diagnose Diabetes? was originally presented Saturday, June 26, and can be viewed by registered meeting attendees at ADA2021.org through September 29, 2021. If you haven’t registered for the Virtual 81st Scientific Sessions, register today to access all of the valuable meeting content.
The 2021 ADA recommendation for using POC A1C for monitoring states: “The use of point-of-care A1C testing may provide an opportunity for more timely treatment changes during encounters between patients and providers.” But for diagnosis, the ADA recommends “only those point-of-care A1C assays that are also cleared by the FDA (U.S. Food and Drug Administration) for use in the diagnosis of diabetes should be used for this purpose, and only in the clinical setting for which they are cleared.”
Jay H. Shubrook, DO, FACOFP, FAAFP, BC-ADM, Professor and Diabetologist, Touro University, supports using POC A1C to diagnose diabetes, noting the sensitivity and specificity of current diagnosis methods vary. POC A1C does not offer the most sensitivity, he noted, but it does offer a rather specific test and the accuracy of POC A1C machines has improved significantly. He cited studies indicating a strong correlation between POC A1C and clinical laboratory measurements.
“I think you should be comfortable that this test can be done and reach comparable accuracy as the laboratory value,” he said.
Dr. Shubrook referenced studies showing that POC A1C is associated with decreases in A1C levels, improved adherence to diabetes guidelines, greater patient satisfaction and confidence in the care process, and an enhanced patient-physician relationship. He also said he appreciates the ability to provide A1C information to patients quickly and in a way that gives them more power to take action.
“This creates a very important, teachable moment where I can start the educational process at the time of diagnosis and not leave a gap of time where somebody sees a result and doesn’t know what it means—or even worse, not getting that result in a timely manner,” Dr. Shubrook said. “It gives me immediate gratification that I know that I’ve closed that loop.”
David B. Sacks, MB ChB, FACP, FRCPath, Chief, Clinical Chemistry Service, National Institutes of Health, identified several disadvantages to POC A1C for diagnosing diabetes. An accurate A1C measurement is required for a diabetes diagnosis, but multiple studies document poor analytic performance of POC A1C devices, with significant differences documented between A1C results obtained by POC devices and lab instruments, he said.
Assay bias has a significant effect on diagnostic accuracy, added Dr. Sacks, citing a meta-analysis of 61 studies of POC A1C versus lab tests in which the A1C assay bias ranged from -0.9 to +0.7.
“If the true (A1C) value is 6.5 and the device has a bias of 0.7, it will tell you that the patient’s A1C is 7.2. Conversely, a negative bias of 0.9 will tell you that patient, who is at the threshold of diagnosis of diabetes, has an A1C of 5.6, which doesn’t even meet current standards for prediabetes,” Dr. Sacks said. “Same patient sample; different instrument.”
In the clinical setting, where trained lab personnel are not doing the testing, results are almost certain to be worse, Dr. Sacks added. He also noted that POC A1C tests are waived tests in the United States. No proficiency testing is required, so there’s no evaluation of the performance of the testing because there is minimal oversight.
Dr. Sacks also noted that blood glucose meters have been in use since 1970, and glucose has been the diagnostic criterion for diabetes even longer.
“Due to lack of accuracy, point-of-care glucose is not accepted for diagnosing diabetes. So why would you accept point-of-care A1C, a newer technology?” Dr. Sacks said.