Definition of hba1c. HbA1c Test: Understanding Glycated Hemoglobin and Diabetes Management

10.07.202303.07.2023 by alexxlab

What is the HbA1c test. How is HbA1c used to diagnose and monitor diabetes. What factors can affect HbA1c results. How often should HbA1c be tested. What are the target HbA1c levels for diabetes management.

Содержание

What is Hemoglobin A1c (HbA1c) and Why is it Important?

Hemoglobin A1c, also known as HbA1c or A1c, is a crucial blood test used to evaluate glucose control in individuals with diabetes. This test provides valuable insights into a person’s average blood sugar levels over the past 90 days, making it an essential tool for diagnosing and managing diabetes.

HbA1c measures the percentage of hemoglobin proteins in red blood cells that have become glycated, or coated with glucose. As blood sugar levels rise, more glucose attaches to hemoglobin, resulting in higher HbA1c levels. This process offers a reliable indicator of long-term blood glucose control.

The Science Behind HbA1c

Hemoglobin is the protein responsible for carrying oxygen throughout the body and giving blood its characteristic red color. Red blood cells have an average lifespan of about three months, which is why the HbA1c test reflects glucose control over this period. The test result is expressed as a percentage, representing the proportion of hemoglobin that has become glycated.

HbA1c as a Diagnostic Tool for Diabetes

The HbA1c test has become an invaluable diagnostic tool for identifying diabetes and prediabetes. Healthcare providers use specific HbA1c ranges to categorize an individual’s glucose control status:

Normal (non-diabetic): HbA1c below 5.7%
Prediabetes: HbA1c between 5.7% and 6.4%
Diabetes: HbA1c of 6.5% or higher

These ranges help clinicians determine appropriate interventions and treatment plans for patients at various stages of glucose control.

Advantages of HbA1c for Diagnosis

Compared to traditional glucose tests, HbA1c offers several advantages for diagnosing diabetes:

No fasting required
Reflects long-term glucose control
Less day-to-day variability
Standardized testing methods

The Role of HbA1c in Diabetes Management

For individuals diagnosed with diabetes, regular HbA1c testing is crucial for monitoring treatment effectiveness and adjusting management strategies. The American Diabetes Association (ADA) recommends specific testing frequencies based on a patient’s glucose control status:

Well-controlled diabetes: HbA1c testing twice a year
Poorly controlled diabetes or recent medication changes: HbA1c testing every 3 months

These guidelines ensure that healthcare providers can make timely adjustments to treatment plans and help patients maintain optimal glucose control.

Target HbA1c Levels for Diabetes Management

Determining appropriate target HbA1c levels is essential for effective diabetes management. While individual goals may vary based on factors such as age, overall health, and risk of complications, general guidelines include:

Adults with diabetes: HbA1c below 7%
Pregnant women with diabetes: HbA1c below 6.5%
Older adults or those with multiple comorbidities: HbA1c between 7.5% and 8.5%

Healthcare providers work closely with patients to establish personalized target levels that balance glucose control with the risk of hypoglycemia and other potential complications.

HbA1c Testing Methods and Procedures

HbA1c testing can be performed using various methods, each with its own advantages and considerations:

Point-of-Care (POC) Testing

POC testing allows for rapid HbA1c results during a patient’s office visit. This method typically uses a small blood sample obtained through a finger prick. While convenient, POC testing may be less accurate than laboratory-based methods and should be confirmed with a venous sample for diagnostic purposes.

Laboratory Testing

Laboratory HbA1c testing is considered the gold standard for accuracy and reliability. This method requires a venous blood sample, usually collected in a lavender-top tube containing K2 EDTA. The sample is processed as whole blood and analyzed using standardized methods approved by the National Glycohemoglobin Standardization Program (NGSP).

Factors Affecting HbA1c Results and Interpretation

While HbA1c is generally a reliable indicator of glucose control, several factors can influence test results and their interpretation:

Medical Conditions

Certain medical conditions can affect HbA1c results, potentially leading to inaccurate readings:

Sickle cell anemia
Thalassemia
Anemia
Kidney failure
Liver disease

In patients with these conditions, HbA1c results should be interpreted cautiously and may need to be confirmed with alternative glucose monitoring methods.

Treatments and Interventions

Various treatments and interventions can impact HbA1c levels, including:

Blood transfusions
Erythropoietin administration
Iron supplementation
Vitamin C supplementation

Healthcare providers should consider these factors when interpreting HbA1c results and making treatment decisions.

Lifestyle and Environmental Factors

Certain lifestyle and environmental factors can also influence HbA1c results:

High altitude
Pregnancy
Alcoholism

Awareness of these potential confounding factors is crucial for accurate interpretation of HbA1c test results.

The Impact of HbA1c Control on Diabetes Complications

Maintaining target HbA1c levels is essential for reducing the risk of diabetes-related complications. Landmark studies, such as the Diabetes Control and Complications Trial (DCCT), have demonstrated the significant impact of glucose control on long-term health outcomes.

Microvascular Complications

Tight glucose control, as reflected by lower HbA1c levels, has been shown to reduce the risk of microvascular complications in patients with diabetes:

Diabetic retinopathy: 35-76% reduction in progression
Diabetic nephropathy: Significant reduction in onset and progression
Diabetic neuropathy: Decreased risk of nerve damage and associated symptoms

Macrovascular Complications

Long-term studies, such as the Epidemiology of Diabetes Interventions and Complications (EDIC) study, have demonstrated that maintaining lower HbA1c levels can also reduce the risk of macrovascular complications:

Cardiovascular disease: Decreased risk of heart attacks and strokes
Peripheral arterial disease: Reduced risk of circulation problems in the extremities

These findings underscore the importance of regular HbA1c monitoring and targeted glucose control in comprehensive diabetes management.

Strategies for Improving HbA1c Levels

For individuals looking to lower their HbA1c levels and improve overall glucose control, several strategies can be effective:

Lifestyle Modifications

Balanced diet: Focus on whole grains, lean proteins, and plenty of fruits and vegetables
Regular physical activity: Aim for at least 150 minutes of moderate-intensity exercise per week
Stress management: Practice relaxation techniques such as meditation or yoga
Adequate sleep: Prioritize 7-9 hours of quality sleep each night

Medication Management

Work closely with healthcare providers to optimize diabetes medication regimens, which may include:

Oral medications: Metformin, sulfonylureas, DPP-4 inhibitors, etc.
Injectable medications: GLP-1 receptor agonists, insulin

Blood Glucose Monitoring

Regular self-monitoring of blood glucose can help individuals make informed decisions about diet, exercise, and medication adjustments. Continuous glucose monitoring (CGM) systems can provide even more detailed insights into glucose patterns and trends.

Education and Support

Participating in diabetes education programs and support groups can provide valuable knowledge, skills, and motivation for improving HbA1c levels and overall diabetes management.

Future Directions in HbA1c Testing and Diabetes Management

As our understanding of diabetes and glucose control continues to evolve, several exciting developments are on the horizon for HbA1c testing and diabetes management:

Advanced Testing Technologies

Researchers are exploring new technologies to improve the accuracy and convenience of HbA1c testing, including:

Non-invasive glucose monitoring devices
Improved point-of-care testing methods
Integration of HbA1c testing with continuous glucose monitoring systems

Personalized Medicine Approaches

The field of diabetes management is moving towards more personalized approaches, taking into account individual genetic, metabolic, and lifestyle factors to optimize treatment strategies and HbA1c targets.

Artificial Intelligence and Machine Learning

Advanced algorithms and data analysis techniques are being developed to predict HbA1c trends, identify individuals at risk for complications, and provide personalized recommendations for improving glucose control.

Novel Therapeutic Approaches

Ongoing research is exploring new treatment modalities that may revolutionize diabetes management and HbA1c control, including:

Gene therapy
Stem cell treatments
Artificial pancreas systems
Gut microbiome interventions

These advancements hold promise for improving the lives of individuals with diabetes and enhancing our ability to achieve and maintain optimal HbA1c levels.

The Importance of Regular HbA1c Monitoring in Diabetes Care

Regular HbA1c monitoring plays a crucial role in comprehensive diabetes care, offering numerous benefits for both patients and healthcare providers:

Early Detection of Glucose Control Issues

Frequent HbA1c testing allows for the early identification of deteriorating glucose control, enabling timely interventions to prevent complications. This proactive approach can significantly improve long-term health outcomes for individuals with diabetes.

Treatment Optimization

HbA1c results provide valuable insights that help healthcare providers fine-tune treatment plans. By tracking HbA1c trends over time, clinicians can make informed decisions about medication adjustments, lifestyle modifications, and other interventions to achieve optimal glucose control.

Patient Empowerment

Regular HbA1c testing empowers patients to take an active role in their diabetes management. By understanding their HbA1c levels and how they relate to daily glucose control, individuals can make informed decisions about their diet, exercise, and medication adherence.

Risk Assessment and Prevention

HbA1c levels serve as a powerful predictor of diabetes-related complications. By monitoring HbA1c regularly, healthcare providers can assess an individual’s risk for developing complications and implement preventive strategies accordingly.

In conclusion, the HbA1c test stands as a cornerstone of modern diabetes management, offering a reliable and comprehensive assessment of long-term glucose control. As research continues to advance our understanding of diabetes and its complications, the role of HbA1c in diagnosis, treatment, and monitoring is likely to evolve, leading to improved outcomes and quality of life for individuals living with diabetes.

Hemoglobin A1C – StatPearls – NCBI Bookshelf

Introduction

The hemoglobin A1c (glycated hemoglobin, glycosylated hemoglobin, HbA1c, or A1c) test is used to evaluate a person’s level of glucose control. The test shows an average of the blood sugar level over the past 90 days and represents a percentage. The test can also be used to diagnose diabetes.[1]

Hemoglobin is a protein only found in red blood cells. In fact, hemoglobin is what gives blood its bright red coloring. Since red blood cells live about an average of three months, the A1c test will reflect those red blood cells that are present in the bloodstream at the time of the test; this is why the A1c serves as an average of blood sugar control.

The main job of hemoglobin is to carry oxygen from the lungs to all the cells of the body. Hemoglobin becomes glycated or coated with glucose from the bloodstream. The amount of glucose that is present in the blood will attach to the hemoglobin protein, and increased glucose levels will reflect on the surface of the hemoglobin protein, thereby rendering a higher A1c level. [2]

Etiology and Epidemiology

The Diabetes Control and Complications Trial (DCCT)[3] was a landmark trial that provided a wealth of data on A1c and its correlation to blood glucose levels, as well as establishing specific treat to target A1c goals. From the completion of the trial, the National Glycohemoglobin Standardization Program (NGSP) was formed to define a standardized assay that was usable across laboratories.

The DCCT trial reported that a higher mean A1c level was the dominant predictor of diabetic retinopathy progression. Tighter control shown by levels of HbA1c in the 7% range or lower, were correlated with 35-76% decrease in microvascular complications, like retinopathy, nephropathy and neuropathy, in patients with type 1 diabetes. In addition to the determination of A1c levels predicting progression of microvascular complications, the extension of DCCT into EDIC study showed benefit in the cardiovascular risk and mortality in the longterm for those patients with lower levels of HbA1c. [4][5][6]

Pathophysiology

People with diabetes need to have their A1c checked regularly to determine if their average blood glucose levels are within the target range. The American Diabetes Association (ADA) recommends that the HbA1c is checked twice a year in patients that are stable and well controlled, versus every 3 months in patients with changes in their medications, or not well controlled. [7]

Specimen Requirements and Procedure

The HbA1c test can either be done as a point of care (POC), STAT test, or by sending a sample to a laboratory. The POC test uses a STAT analyzer that evaluates the A1c from a capillary fingerstick. The laboratory test uses a teaspoon of blood drawn from a venous sample into a K2 EDTA (lavender top) tube. The sample gets processed as whole blood.

Diagnostic Tests

The venous sample A1c test may be used as a diagnostic tool in clinical practice when determining diabetes risk or onset. Due to the variability of capillary point of care testing, any A1c done by capillary sample should be confirmed with a venous sample before rendering the diagnosis.

For an HbA1c test to classify as normal, or in the non-diabetic range, the value must be below 5.7 %. Anyone with an HbA1c value of 5.7 % to 6.4 % is considered to be prediabetic, while diabetes can be diagnosed with a HbA1c of 6.5% or higher.

Tests should be sent to a laboratory certified by the NGSP to ensure results are standardized.[8][9]

Testing Procedures

The HbA1c test done by a point of care machine in a doctor’s office may be less accurate than one that is drawn from a venous sample and processed in a laboratory. Typically, the results can vary by different laboratories by as much as 0.5%.

The HbA1c test should be performed using an NGSP-approved method.

Interfering Factors

There are several conditions where the HbA1c test can produce inaccurate results. People diagnosed with sickle cell anemia, thalassemia, anemia, kidney failure, liver disease, or patients receiving blood transfusions can experience altered results due to the longevity of the red blood cell. HbA1c measurement in these patients must be interpreted with caution and should be confirmed with plasma glucose samples to diagnose diabetes.[10]

A falsely low HbA1c value can result from several conditions including high altitude, pregnancy, hemorrhage, blood transfusion, erythropoietin administration, iron supplementation[11], hemolytic anemia, chronic kidney failure, liver cirrhosis, alcoholism, sickle cell anemia[12], and spherocytosis. Vitamin C supplementation can either increase or decrease the HbA1c level depending on the method used for its measurement.[15]

On the other end of the spectrum, a falsely high HbA1c can be due to a lack of available iron in the blood. This condition can result from iron deficiency anemia[13], infection-induced anemia, or tumor-induced anemia. Hemoglobinopathies such as thalassemia and B12 deficiency[11][14] can also cause a falsely high HbA1c. Other causes of falsely high HbA1c levels include hypertriglyceridemia, organ transplantation, and hyperglycation in certain ethnic groups. Medications such as immunosuppressants and protease inhibitors can sometimes lead to a falsely high HbA1c.[10][7][15][16]

Results, Reporting, and Critical Findings

Relationship Between A1c and Glucose Level

The HbA1c percentage equates to an average glucose level in the body that the patient experienced over the past 90 days.[17][18][19]

A1c (%) Average Blood Glucose (mg/dL)

6 126

8 183

10 240

12 298

14 355

Clinical Significance

Hemoglobin A1c serves as an indicator of overall glycemic control and a reflection of the average blood sugar over the past three months.[2]

Quality Control and Lab Safety

Laboratories can use several methods to determine HbA1c. High performance liquid chromatography (HPLC) method is one of the most popular methods because it can eliminate labile components that other methods such as immunoassay or affinity chromatography use. [20]

The point of care (POC) machine is widely used as well to determine HbA1c levels. The variety of POC machines on the market can make it difficult to determine the one best suited for one’s practice. Also, there is a shortage of information comparing the different machines. When using POC testing, one should keep in mind that POC values are often below results reported by a laboratory test, with the mean difference being -0.5%.

Enhancing Healthcare Team Outcomes

All clinicians who look after diabetic patients need to know what HbA1c means. In general, HbA1c provides a measure of the average glucose concentration over three months.

Hemoglobin A1c is often used as an outcome measure to determine if an intervention in a population is successful by showing a decrease in HbA1c by a certain percentage. There is a movement within the medical community to move away from using HbA1c as an exclusive standard of care test to measure patient response to treatment. The Estimated Average Glucose (eAG) and the glucose time in range are the newest proposed methods. [21] These methods use data obtained by continuous glucose monitors (CGMs) that record blood glucose 24 hours a day. They can also give providers a more accurate view of the blood sugar average and fluctuations, but these methods are not available to all patients on a wide-spread basis.

As per ADA guidelines, the levels of HA1c should be measured twice a year in stable patients and at least four times in patients who have glucose fluctuations or those who have had a change in their diabetic treatment. Hemoglobin A1c is one of the preferred diabetes diagnostic tests today. The blood draw can occur at any time, and there are no special handling requirements. However, to ensure that the A1c value is correct, clinicians need to be aware of the causes of false-positive and false-negative results.

Since many patients with diabetes have their condition managed in outpatient clinics, the diabetic nurse should be fully aware of HbA1c values and when to refer the patient to an endocrinologist for further workup and treatment. Pharmacists are also required to fully understand and interpret this test, as they will be involved in glycemic management medication agent selection, dosing, and monitoring. Both the nurse and/or pharmacist need to inform the treating physician regarding any changes in hemoglobin A1c and verify patient medication compliance. Hemoglobin A1c is a very valuable tool in the fight against diabetes and other glycemic control disorders, but to be effective, it functions best in an interprofessional healthcare team environment. [Level V]

Review Questions

Access free multiple choice questions on this topic.
Comment on this article.

References

1.: Gilstrap LG, Chernew ME, Nguyen CA, Alam S, Bai B, McWilliams JM, Landon BE, Landrum MB. Association Between Clinical Practice Group Adherence to Quality Measures and Adverse Outcomes Among Adult Patients With Diabetes. JAMA Netw Open. 2019 Aug 02;2(8):e199139. [PMC free article: PMC6694385] [PubMed: 31411713]
2.: Sherwani SI, Khan HA, Ekhzaimy A, Masood A, Sakharkar MK. Significance of HbA1c Test in Diagnosis and Prognosis of Diabetic Patients. Biomark Insights. 2016;11:95-104. [PMC free article: PMC4933534] [PubMed: 27398023]
3.: Diabetes Control and Complications Trial Research Group. Nathan DM, Genuth S, Lachin J, Cleary P, Crofford O, Davis M, Rand L, Siebert C. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993 Sep 30;329(14):977-86. [PubMed: 8366922]
4.: Nathan DM., DCCT/EDIC Research Group. The diabetes control and complications trial/epidemiology of diabetes interventions and complications study at 30 years: overview. Diabetes Care. 2014;37(1):9-16. [PMC free article: PMC3867999] [PubMed: 24356592]
5.: Nathan DM. Realising the long-term promise of insulin therapy: the DCCT/EDIC study. Diabetologia. 2021 May;64(5):1049-1058. [PubMed: 33550441]
6.: Lachin JM, Orchard TJ, Nathan DM., DCCT/EDIC Research Group. Update on cardiovascular outcomes at 30 years of the diabetes control and complications trial/epidemiology of diabetes interventions and complications study. Diabetes Care. 2014;37(1):39-43. [PMC free article: PMC3868002] [PubMed: 24356596]
7.: American Diabetes Association. 6. Glycemic Targets: Standards of Medical Care in Diabetes-2021. Diabetes Care. 2021 Jan;44(Suppl 1):S73-S84. [PubMed: 33298417]
8.: American Diabetes Association. 6. Glycemic Targets: Standards of Medical Care in Diabetes-2019. Diabetes Care. 2019 Jan;42(Suppl 1):S61-S70. [PubMed: 30559232]
9.: Qaseem A, Wilt TJ, Kansagara D, Horwitch C, Barry MJ, Forciea MA, Clinical Guidelines Committee of the American College of Physicians. Fitterman N, Balzer K, Boyd C, Humphrey LL, Iorio A, Lin J, Maroto M, McLean R, Mustafa R, Tufte J. Hemoglobin A1c Targets for Glycemic Control With Pharmacologic Therapy for Nonpregnant Adults With Type 2 Diabetes Mellitus: A Guidance Statement Update From the American College of Physicians. Ann Intern Med. 2018 Apr 17;168(8):569-576. [PubMed: 29507945]
10.: Heinemann L, Freckmann G. Quality of HbA1c Measurement in the Practice: The German Perspective. J Diabetes Sci Technol. 2015 May;9(3):687-95. [PMC free article: PMC4604529] [PubMed: 25691655]
11.: Pilla R, Palleti SK, Rayana R, Skss SR, Abdul Razzack A, Kalla S. Glycated Haemoglobin (HbA1c) Variations in Nondiabetics With Nutritional Anemia. Cureus. 2020 Nov 13;12(11):e11479. [PMC free article: PMC7735166] [PubMed: 33329975]
12.: Lacy ME, Wellenius GA, Sumner AE, Correa A, Carnethon MR, Liem RI, Wilson JG, Sacks DB, Jacobs DR, Carson AP, Luo X, Gjelsvik A, Reiner AP, Naik RP, Liu S, Musani SK, Eaton CB, Wu WC. Association of Sickle Cell Trait With Hemoglobin A1c in African Americans. JAMA. 2017 Feb 07;317(5):507-515. [PMC free article: PMC5713881] [PubMed: 28170479]
13.: Guo W, Zhou Q, Jia Y, Xu J. Increased Levels of Glycated Hemoglobin A1c and Iron Deficiency Anemia: A Review. Med Sci Monit. 2019 Nov 07;25:8371-8378. [PMC free article: PMC6857442] [PubMed: 31696865]
14.: Gram-Hansen P, Eriksen J, Mourits-Andersen T, Olesen L. Glycosylated haemoglobin (HbA1c) in iron- and vitamin B12 deficiency. J Intern Med. 1990 Feb;227(2):133-6. [PubMed: 2299304]
15.: Radin MS. Pitfalls in hemoglobin A1c measurement: when results may be misleading. J Gen Intern Med. 2014 Feb;29(2):388-94. [PMC free article: PMC3912281] [PubMed: 24002631]
16.: Shepard JG, Airee A, Dake AW, McFarland MS, Vora A. Limitations of A1c Interpretation. South Med J. 2015 Dec;108(12):724-9. [PubMed: 26630892]
17.: van ‘t Riet E, Alssema M, Rijkelijkhuizen JM, Kostense PJ, Nijpels G, Dekker JM. Relationship between A1C and glucose levels in the general Dutch population: the new Hoorn study. Diabetes Care. 2010 Jan;33(1):61-6. [PMC free article: PMC2797987] [PubMed: 19808928]
18.: Sayed A, Alyafei F, De Sanctis V, Soliman A, Elgamal M. Translating the HbA1c assay into estimated average glucose values in children and adolescents with type 1 diabetes mellitus. Acta Biomed. 2018 May 23;89(S5):22-26. [PMC free article: PMC6179094] [PubMed: 30049928]
19.: Lai LC. Global standardisation of HbA1c. Malays J Pathol. 2008 Dec;30(2):67-71. [PubMed: 19291914]
20.: Kawano K. Quality control, quality assessment of laboratory tests, HbA1c. Southeast Asian J Trop Med Public Health. 1999;30 Suppl 3:117-21. [PubMed: 10926271]
21.: Saboo B, Kesavadev J, Shankar A, Krishna MB, Sheth S, Patel V, Krishnan G. Time-in-range as a target in type 2 diabetes: An urgent need. Heliyon. 2021 Jan;7(1):e05967. [PMC free article: PMC7814148] [PubMed: 33506132]

: Disclosure: Emily Eyth declares no relevant financial relationships with ineligible companies.
: Disclosure: Roopa Naik declares no relevant financial relationships with ineligible companies.