Blood Glucose Control, DM Diagnosis, and the Glycated Hemogobin A1c Test

Friday, July 26, 2013

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Diabetes Epidemiology

A little over 8% of the population in the U.S. has diabetes mellitus (DM), with about 27% of these cases not diagnosed. Type 1 DM is an autoimmune disease, accounting for about 5% of cases. Effective treatment requires insulin. Type 2 DM accounts for 90% to 95% of cases, and rates vary by race and ethnicity.1 Type 2 DM can be prevented by diet, physical activity, and weight loss. There are oral medications to treat type 2 DM, and insulin might also be necessary. Diabetes that occurs during pregnancy (gestational diabetes) is more common in certain races, and is also associated with obesity or with a family history of type 2 DM. It requires treatment to avoid complications in the infant.

The rates of type 1 and 2 DM have been increasing both in the U.S. and worldwide. Type 2 DM in particular has been increasing in developing countries, along with the increased rates of obesity and westernization of lifestyle. The International Diabetes Federation has predicted that the number of people living with diabetes will increase from 366 million in 2011 to 552 million in 2030.2

The complications of untreated and poorly controlled diabetes ultimately lead to kidney disease, cardio- and peripheral vascular disease, and neuropathy. Based on U.S. death certificates in 2007, diabetes was the seventh leading cause of death (71,382 deaths). It is also a contributing cause of death in 160,022 deaths, and is probably underreported, as 35% to 40% of death certificates list diabetes somewhere on the death certificate. The risk for death among people with diabetes is about twofold greater than for people of a similar age without diabetes.3 The estimated economic burden in 2007 was $174 billion, which included direct and indirect costs.3

HbA1c Testing is Now for Both Diagnosing and Monitoring Diabetes

It is now widely accepted that intensive control of blood sugar delays the onset of serious diabetic complications. The hemoglobin A1c (HbA1c) test is recommended by the American Diabetes Association (ADA) as the best way to monitor a patient’s blood glucose control. HbA1c refers to glycation of the beta chain of hemoglobin A by a sugar moiety. Because HbA1c is stable, measurement of its concentration in the blood reflects the mean level of glucose over the life span of a red blood cell, which is normally about 120 days. The HbA1c test is also now recommended by the ADA as the preferred diagnostic test for DM.4 Although the upper limit of normal is considered to be 6% to <6.5%, HbA1c values between 5.5% and 6.0% most accurately identify individuals with impaired fasting or glucose tolerance; these people are at very high risk of developing diabetes.

Most HbA1c tests have been standardized worldwide to the assay used in the Diabetes Controls and Complications Trial. However, a newer method, which is more stable and specific, yields results that are 1.5% to 2.0% lower than the older values. Countries have resolved the differences by either adopting new units (mmol/mol) or by using conventional units (%). Since the trend is to use the new units, many laboratories are reporting the estimated average glucose (EAG [mg/dL]) along with every HbA1c level (%).5

Testing is Convenient, Yielding Rapid HbA1c Results

HbA1c testing is advantageous to the patient. No fasting is needed. Because it is very stable, a blood sample can be collected at the clinical laboratory or at the point of care.

  • Bio-Rad Laboratories, Inc. (Hercules, CA) offers the D-10™ Hemoglobin Testing System, which consists of a compact hemoglobin analyzer and accessories for diabetes testing and β-thalassemia on a single platform. It can be used in clinics, physicians’ offices, or clinical laboratories. It features an automated-system startup checklist, touchscreen operation, and whole-blood primary tube sampling. There are separate programs for fast HbA1c testing or testing for both thalassemia and HbA1c. With the addition of the D-10 Rack Loader, the capacity of the system can be increased to 50 whole-blood samples.
  • EKF Diagnostics (Cardiff, U.K.) offers the CE-marked Quo-Test® HbA1c Analyser, which uses boronate-fluorescence-quenching technology to measure glycated hemoglobin from a 4-μL sample taken from a finger prick or venous whole blood. The sample collector is inserted into the Quo-Test cartridge, which is inserted into the analyser. Results are displayed within 4 min. The measuring range is 4% to 15% HbA1c.
  • Axis-Shield USA (Norton, MA) offers the CLIA-waived Afinion™ Test Cartridge, which is used to test HbA1c on the Afinion AS100 Analyzer. The test cartridges come in kits of 15, and are used to directly sample blood from a finger stick. The sample size is 1.5 μL, and test results are available in less than 4 min.

References

  1. Diabetes: Successes and opportunities for population-based prevention and control: at a glance, 2011; http://www.cdc.gov/chronicdisease/resources/publications/AAG/ddt.htm.
  2. http://www.idf.org/media-events/press-releases/2011/diabetes-atlas-5th-edition.
  3. National Diabetes Fact Sheet, 2011; http://www.cdc.gov/diabetes/pubs/pdf/ndfs_2011.pdf.
  4. American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care 2010, 33(Suppl 1), S62–S9.
  5. Nathan, D.M.; Kuenen, J. et al. Translating the A1C assay into estimated average glucose values. Diabetes Care  2008, 31, 1–6.

Please see our Clinical Diagnostics Assays section and Blood Chemistry Analyzer / Blood Analyzers section to find manufacturers that sell these products