EDUCATON :: DIABETES
such as sodium fluoride, should be avoided. Granulated citrate is the optimum inhibitor, the committee says. However, if the appropriate tubes are not available, the ice-
water slurry is a reasonable second choice, according to the 2021 AACC presentation. “There’s more evidence to support that — a lot of studies
have been done using a granular citrate as a buffer and showing that it’s very effective,” Sacks said. “Ten years ago, when we published the previous version of this guideline, that evidence was not available. So that’s a classic example of how the guidelines change in response to new evidence,” he said.
Unfortunately, tubes with granulated citrate are not avail- able in the United States, Sacks said, adding that he is hopeful manufacturers will respond to the recommendation by produc- ing and selling them.
Testing women during pregnancy
Another area of emphasis in the 2021 draft guidelines is diabetes testing in pregnant and postpartum women. The recommendations are as follows:
• All pregnant women with risk factors for diabetes should be tested for undiagnosed prediabetes and diabetes at the first prenatal visit using standard diagnostic criteria.
• All pregnant women not previously known to have diabetes should be evaluated for gestational diabetes between 24-28 weeks of gestation.
• Women with gestational diabetes should be tested for diabetes 4-12 weeks postpartum using non-pregnant criteria. Why the emphasis? “Diabetes has such a huge impact on the pregnancy, so it’s important to pick this up and manage patients in the early stages of pregnancy,” Sacks says, noting that many people with diabetes are not aware that they have it. Approximately 30% of women of childbearing age have impaired glucose metabolism, according to the committee’s AACC presentation. Because women who have had gestational diabetes are at higher risk of contracting type 2 diabetes later in life, it also is important to start monitoring them in the postpartum stage, he says.
Continuous glucose monitors The committee also focused on continuous glucose monitors. As is often the case with technology, continuous glucose monitors (CGMs) have advanced significantly since 2011. The systems, which measure interstitial glucose concentra-
M. Sue Kirkman, MD
tions every 5-15 minutes, are much more accurate than they were in 2011. Most of the monitors now are approved by the U.S. Food and Drug Administration (FDA) for use when patients are making decisions about insulin dosing without the use of a fingerstick test, explains M. Sue Kirkman, MD, Professor of Medicine at University of North Carolina School of Medicine, an expert on the monitors and a member of the committee. The continuous glucose meters also now are helpful to a broader range of people. “Since 2011, we’ve also seen a lot
more randomized trials of CGM showing benefits in broader populations beyond what we had in 2011 (when we mainly had evidence for benefit in adults with type 1 diabetes.) More recent studies have shown benefit on HbA1c and/or hypoglycemia in teens with type 1 diabetes, older people with type 1 diabetes
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and a lot of hypoglycemia, pregnant women with type 1, people with type 2 on insulin, and others,” Kirkman said. When asked why the committee does not recommend the use of the devices to diagnose diabetes, Kirkman said, “One problem is that we don’t know what cut-points we would use. We could get an average for interstitial glucose, but what does that add beyond HbA1c? And accuracy may not be high enough (analogous to not recommending meter glucose to diagnose diabetes). Also, a person has to wear a CGM for 72 hours or more to get enough data to be meaningful in terms of what ‘average’ glucose is. With tests like fasting plasma glucose or HbA1c being so quick, there doesn’t seem to be a good reason to do this.”
HbA1c
HbA1c measurement also is a subject covered in the draft guide- lines, addressing the role of interferences that compromise the results of HbA1c tests. The recommendations are as follows: • Assays of other glycated proteins, such as fructosamine or glycated albumin, may be used in clinical settings where abnormalities in red cell turnover, hemoglobin variants or other interfering factors compromise interpretation of HbA1c test results, although they reflect a shorter period of glycemia than HbA1c.
• HbA1c values that are inconsistent with the clinical presen- tation should be investigated further, including whether interfering factors are present.
• Comparison of suspicious HbA1c results with other glycated protein assays may be informative. Common hemoglobin variants include HbS, which leads to
Sickle cell anemia; HbC, which causes mild hemolytic anemia and mild to moderate enlargement of the spleen; and HbE, which causes mild hemolytic anemia, microcytosis, and mild enlargement of the spleen.3 HbA1c, which is used to both monitor blood sugar control in existing diabetes cases and to diagnose new cases, also is another perfect example of the importance of standardizing testing processes through adherence to clinical guidelines, Bruns explains. “The difference between HbA1c that is normal and one that isn’t is extremely small. We’re talking about tenths of a percent. We have to be able to hit that level of accuracy day in and day out around the clock, 365 days a year in thousands of clinical laboratories. Standardization is absolutely critical because the analyte itself is difficult to measure,” he said. Whether it is a recommendation related to HbA1c or another
aspect of diabetes diagnosis and monitoring, Sacks says when the guidelines are finalized, he expects that clinical laboratories will revise their testing practices to align with the new recom- mendations. “As knowledge and technology improves one would hope that clinical labs would incorporate the latest knowledge and the latest testing,” he said.
REFERENCES
1. Centers for Disease Control and Prevention. National diabetes statistics report, 2020.
https://www.cdc.gov/diabetes/pdfs/data/statistics/national- diabetes-statistics-report. Accessed October 31, 2022.
2. Sacks D, Arnold M, Bakris G, Bruns, D et al. Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Diabetes Care. 2011. June; 34(6): e61-e99. doi: 10.2337/dc11-9998
3. Sivaraman P. The role of race and ethnicity in variant hemoglobin. Medi- cal Laboratory Observer.
https://www.mlo-online.com/disease/diabetes/ article/21203094/the-role-of-race-and-ethnicity-in-variant-hemoglobin-traits. December 22, 2020. Accessed October 31, 2021.
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