Diagnosing and monitoring diabetes: What is HbA1c and how can it build upon traditional glucose testing methods?
Diabetes mellitus is a common group of metabolic disorders; with a global prevalence of around 8.5%, or approximately 422 million people according to the World Health Organization (WHO) in 2014.1
Characterized by frequent periods of uncontrolled hyperglycemia, diabetes is split into two main types: type 1 and type 2. Type 1 diabetes is characterized by a deficiency of insulin production from the pancreas, which leads to uncontrolled levels of blood glucose. Type 2 diabetes, the most common form, involves either the pancreas not producing enough insulin or the body’s cells becoming resistant to the action of insulin.
Diabetes Testing Methods - FBG and OGTT
The gold standard diagnostic method for diabetes has previously been the measurement of either fasting blood glucose (FBG) or two-hour plasma glucose via an oral glucose tolerance test (OGTT).2
The diagnostic criteria for a patient to be considered diabetic using FBG or OGTT is:
- FBG ≥7.0 mmol/l, or
- Two-hour plasma blood glucose concentration must be ≥11.1 mmol/l two hours following administration of a 75g anhydrous glucose via an OGTT
Although both testing methods provide a good level of accuracy, they present their own limitations. Both tests rely on a suitable application of the test within specific time periods and compliance from the patient.
Pre-test preparation for testing two-hour plasma blood glucose concentration, for example, includes providing patients with a strict diet for three days prior to testing and overnight fasting.
While the FBG test requires a minimum of 8 hours of fasting before the test can be completed. Overall, traditional diagnostic methods can seem daunting and time consuming, which makes patient compliance difficult to achieve.
The requirement to fast with traditional glucose testing methods can bea potentially difficult compliance standard to meet for some, especially those already struggling with glycemic control. Some patients may consume food or beverages (aside from water) within the fasting period, believing this small action would not affect the testing results but in reality this would usually mean the test would have to be repeated.
The OGTT relies on the patient remembering to adhere to the conditions of the test during the two-hour period, and there is a chance that the patient will fail to return to the testing location in the appropriate time frame to obtain accurate results.
Hemoglobin, a protein in red blood cells, is used to bond with oxygen and transport it around the body, but can also bond with glucose in the bloodstream, resulting in glycated hemoglobin or HbA1c.
Glycation is irreversible, so HbA1c remains in this state in the red blood cell for around eight to twelve weeks, the lifespan of the red blood cell. The more HbA1c found within the blood, the greater the chance the patient has diabetes or is at risk for developing the disorder.
Diabetes onset, particularly type 2 diabetes, tends to be slow, with small and gradual increases in blood glucose levels over time.3 Early and accurate diagnostic techniques are essential for improving patient care.
Glycated hemoglobin is a diagnostic approach that provides insight into chronic hyperglycemia rather than testing glucose in a fasting state or over a two-hour time period.
Using this diagnostic tool, the glycemic index is tested for the 120-day lifespan of the red blood cell.4 The HbA1c method, therefore, may stratify risk as well as provide a firm diabetes diagnosis.
In 2009, the International Expert Committee recommended the diagnostic criteria of HbA1c to be introduced at a threshold of ≥48 mmol/mol (≥6.5%).5 The WHO as well as the American Diabetes Association adopted the recommendation of HbA1c for diabetes testing, stating that an HbA1c of 6.5% or more is the cut-off point for a diabetes diagnosis.6
Additionally, the WHO approved the use of Point-of-Care-Testing (POCT) devices for HbA1c diagnostic techniques traceable to the International Federation of Clinical Chemistry (IFCC) reference method. The Quo-Test® analyzer by EKF Diagnostics, for example, is a POCT analyzer which directly measures HbA1c in minutes using a 4 μl sample of blood from a simple finger prick.
Prior to POCT devices, HbA1c tests provided little to no time or value advantage over traditional diagnostic strategies. Using systems like EFK Diagnostics’ Quo-Lab® A1c Analyzer, however, researchers can quickly gain insight into a patient’s risk for diabetes and pre-diabetes. With diagnosis in minutes, earlier treatment can occur. Early treatment is ideal as it may reduce long-term deleterious effects, including worsening glycemic function and blood vessel damage.7
Using HbA1c as a diagnostic marker for diabetes may promote a higher rate of patient compliance, given the minimal preparation associated with the test. Only one blood sample is used, providing accurate initial results without necessitating repeat testing.
Considering that a large proportion of the population with diabetes or prediabetes go undiagnosed, HbA1c testing may reduce global morbidity associated with the disorder.10
However, there are a few patient groups who are not desirable candidates for HbA1c testing, including pregnant women, children, and patients with a history of acute pancreatic damage or pancreatic surgery.11
Learn more about Hba1c testing
Read more about EKF Diagnostics’ approved POCT devices for Hba1c testing as well as their suite of glucose analyzers, including the Biosen C-Line glucose analyzer, Quo-Lab® A1c Analyzer, and Quo-Test® analyzer.
- Global report on diabetes. World Health Organization. http://www.who.int/diabetes/global-report/en/.
- American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2010;33 Suppl 1:S62-S69.
- Florkowski C. HbA1c as a Diagnostic Test for Diabetes Mellitus - Reviewing the Evidence. Clin Biochem Rev. 2013;34(2):75-83.
- Sacks DB. Correlation between hemoglobin A1c (HbA1c) and average blood glucose: can HbA1c be reported as estimated blood glucose concentration? J Diabetes Sci Technol. 2007;1(6):801-803.
- International Expert Committee. International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care. 2009;32(7):1327-1334.
- Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus. World Health Organization. http://www.who.int/cardiovascular_diseases/report-hba1c_2011_edited.pdf.
- Romanelli RJ, Chung S, Pu J, et al. Comparative effectiveness of early versus delayed metformin in the treatment of type 2 diabetes. Diabetes Res Clin Pract. 2015;108(1):170-178.
- Crawford SO, Hoogeveen RC, Brancati FL, et al. Association of blood lactate with type 2 diabetes: the Atherosclerosis Risk in Communities Carotid MRI Study. Int J Epidemiol. 2010;39(6):1647-1655.
- Wu Y, Dong Y, Atefi M, et al. Lactate, a Neglected Factor for Diabetes and Cancer Interaction. Mediators Inflamm. 2016;2016:6456018.
- Dunstan DW, Zimmet PZ, Welborn TA, et al. The rising prevalence of diabetes and impaired glucose tolerance: the Australian Diabetes, Obesity and Lifestyle Study. Diabetes Care. 2002;25(5):829-834.
- John WG. Use of HbA1c in the diagnosis of diabetes mellitus in the UK. The implementation of World Health Organization guidance 2011. Diabet Med. 2012;29(11):1350-1357.