New Guidelines on Diabetes-Related Laboratory Testing

New guidelines from the American Association of Clinical Chemistry (AACC) and American Diabetes Association (ADA) address laboratory measures in the diagnosis and management of diabetes.

The document, entitled, “Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus,” is primarily aimed at both laboratory professionals and clinicians involved in diabetes care.

The guidance is focussed “on the practical aspects of care in order to assist with decisions regarding the use or interpretation of laboratory tests while screening, diagnosing, or monitoring patients with diabetes,” write David B. Sacks, MBChB, chief of the clinical chemistry service at the National Institutes of Health (NIH), Bethesda, Maryland, and co-authors. It was published online July 20 in both Clinical Chemistry and Diabetes Care, including the guidelines and executive summary.  

Co-author M. Sue Kirkman, MD, of the University of North Carolina, Chapel Hill, told Medscape Medical News: “One objective of the guidelines is to increase clinicians’ understanding of the strengths and limitations of tests done in a laboratory and also at the point of care, or in daily life, by people with diabetes.”

The evidence-based recommendations, an update of prior versions published in 2011 and 2002, are meant as a supplement to the ADA Standards of Care in Diabetes and do not address aspects of clinical management, she stressed.

Addition of Advice on CGM

A significant addition since 2011 is detailed information regarding the use of real-time continuous glucose monitoring (CGM), with a “strong” recommendation based on a “high” level of evidence for use in teens and adults with type 1 diabetes who meet certain criteria, and lower-grade advice to use real-time or intermittently scanned CGM in other populations, including children with diabetes, pregnant women with type 1 diabetes, and adults with type 2 diabetes taking insulin.

The document also reminds clinicians to consider test limitations, Kirkman pointed out.

“We do a lot of testing in screening, diagnosis, and monitoring of diabetes and its complications, yet for many clinicians we think that any result we get — or that a patient gets from home testing — is perfect. We often don’t think about the accuracy or precision of some tests, things that might interfere with the result, intra-individual variation of the test, or how one test may compare to a test of higher accuracy,” she said.

One example is a recommendation to collect blood samples for glucose analysis in tubes containing a rapidly effective inhibitor of glycolysis such as a granulated citrate buffer. If unavailable, the sample tube should be placed immediately into an ice water slurry and centrifuged within 15-30 minutes to remove the cells.

Without those measures, “red cells in blood sitting in the test tube continue to break down glucose, so the concentration of glucose will start to fall very soon…How the specimen is handled makes a huge difference in the result,” Kirkman emphasized.

Another is the recommendation of a confirmatory test when diagnosing diabetes, regardless of the initial test used (A1c, fasting glucose, or oral glucose tolerance test). “There is large intra-individual variation of fasting glucose and even larger for 2-hour glucose on the oral glucose tolerance test…This means if you do the test one week and then repeat it the next day or a week later, the results will be quite different. This is a reason why confirmation of an abnormal test is important. Yet many times this isn’t done,” she noted.

Other “strong” recommendations based on “high” evidence levels include:

• Fasting glucose should be measured in venous plasma when used to establish the diagnosis of diabetes, with a diagnostic cutoff of > 7.0 mmol/L (> 126 mg/dL) for diabetes.

• Frequent blood glucose monitoring is recommended for all people with diabetes treated with intensive insulin regimens (with multiple daily injections or insulin pump therapy) and who are not using CGM.

• Routine use of blood glucose monitoring is not recommended for people with type 2 diabetes who are treated with diet and/or oral agents alone.

• Treatment goals should be based on ADA recommendations, ie A1c < 7% (< 53 mmol/mol) if it can be achieved without significant hypoglycemia or other adverse treatment effects, with higher targets for special populations.

• Annual testing for albuminuria should begin in pubertal or post-pubertal individuals 5 years after diagnosis of type 1 diabetes and at time of diagnosis of type 2 diabetes, regardless of treatment.

• Urine albumin should be measured annually in adults with diabetes using morning spot urine albumin-to-creatinine ratio.

Other guidance in the document pertains to use of ketone testing, genetic markers, autoimmune markers, and C-peptide.

According to Sacks, “It’s important to measure accurately, but it’s also very important to communicate the relevance to clinicians and to listen to them and share information…Patient care is a team effort.”

Sachs has reported receiving funding from the NIH. Kirkman has reported no relevant financial relationships.

Clin Chem. Published online July 20, 2023. Full text

Diabetes Care. Published online July 20, 2023. Guidelines, Executive summary  

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in The Washington Post, NPR’s Shots blog, and Diabetes Forecast magazine. She is on Twitter: @MiriamETucker.

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