What is glycosylated hemoglobin. How is HbA1c used in diabetes management. What are the normal ranges for HbA1c. How is glycosylated hemoglobin formed. What are the implications of high HbA1c levels. How often should HbA1c be tested in diabetic patients. What factors can affect HbA1c results.

Understanding Glycosylated Hemoglobin: The Basics of HbA1c

Glycosylated hemoglobin, commonly known as hemoglobin A1c (HbA1c), is a crucial biomarker in the management of diabetes. This form of hemoglobin provides valuable insights into long-term blood glucose control, making it an essential tool for healthcare providers and patients alike.

How is glycosylated hemoglobin formed? When glucose molecules in the bloodstream attach to hemoglobin proteins in red blood cells, they create glycated hemoglobin. This process occurs naturally and continuously throughout the 120-day lifespan of red blood cells.

The Science Behind HbA1c

The formation of glycosylated hemoglobin is a non-enzymatic process that results from the normal exposure of hemoglobin to high plasma glucose levels. As glucose levels in the blood increase, so does the percentage of hemoglobin that becomes glycated. This relationship allows healthcare providers to use HbA1c as a reliable indicator of average blood glucose levels over an extended period.

The Historical Journey of HbA1c in Diabetes Management

The discovery and application of glycosylated hemoglobin in diabetes management have a rich history spanning several decades. This journey highlights the importance of scientific breakthroughs in improving patient care.

• 1958: Huisman and Meyering first separate HbA1c from other hemoglobin forms using chromatography
• 1968: Bookchin and Gallop characterize HbA1c as a glycoprotein
• 1969: Samuel Rahbar and colleagues describe the increase of HbA1c in diabetes
• 1975: Bunn and co-workers characterize the reactions leading to HbA1c formation
• 1976: Koenig and co-workers propose using HbA1c to monitor glucose metabolism in diabetic patients

This timeline demonstrates the gradual understanding of HbA1c’s role in diabetes, leading to its widespread adoption as a key diagnostic and monitoring tool.

The Role of HbA1c in Diabetes Diagnosis and Monitoring

HbA1c testing has revolutionized diabetes management by providing a more comprehensive view of blood glucose control compared to traditional blood glucose measurements. Why is HbA1c preferred over daily glucose testing? Unlike daily glucose tests, which offer a snapshot of blood sugar levels at a specific moment, HbA1c reflects average glucose levels over a 2-3 month period.

Advantages of HbA1c Testing

• Provides a long-term view of glucose control
• Doesn’t require fasting
• Less affected by short-term lifestyle changes
• Helps predict the risk of diabetes complications

These advantages make HbA1c an invaluable tool for both diagnosing diabetes and monitoring treatment efficacy in diagnosed patients.

Interpreting HbA1c Results: What Do the Numbers Mean?

Understanding HbA1c results is crucial for effective diabetes management. The test results are typically expressed as a percentage, representing the proportion of hemoglobin that has become glycated.

HbA1c Ranges and Their Implications

• Normal range: 4% – 5.6%
• Prediabetes: 5.7% – 6.4%
• Diabetes: 6.5% or higher

What do these ranges signify for patients? A result within the normal range suggests that blood glucose levels have been well-controlled over the past 2-3 months. Prediabetic levels indicate an increased risk of developing type 2 diabetes, while results of 6.5% or higher are diagnostic of diabetes.

Target HbA1c Levels for Diabetic Patients

For individuals diagnosed with diabetes, maintaining HbA1c levels within a target range is essential for minimizing the risk of complications. Different organizations provide slightly varying recommendations:

• American Diabetes Association: Below 7% for most patients
• International Diabetes Federation: Below 6.5%
• American College of Endocrinology: Below 6.5%

These targets may be adjusted based on individual patient factors such as age, overall health status, and risk of hypoglycemia.

The Relationship Between HbA1c and Average Blood Glucose Levels

One of the most valuable aspects of HbA1c testing is its ability to provide an estimate of average blood glucose levels over time. This relationship allows healthcare providers and patients to better understand glucose control without the need for frequent blood glucose monitoring.

HbA1c to Average Blood Glucose Conversion

The following table illustrates the approximate correlation between HbA1c percentages and average blood glucose levels:

This correlation helps patients and healthcare providers set realistic goals for blood glucose management and understand the impact of daily glucose fluctuations on long-term control.

Factors Affecting HbA1c Results: Beyond Blood Glucose

While HbA1c is primarily influenced by blood glucose levels, several other factors can impact test results. Understanding these factors is crucial for accurate interpretation of HbA1c values.

Conditions That May Affect HbA1c Readings

• Red blood cell lifespan: Conditions that shorten red blood cell lifespan (e.g., hemolytic anemia) can lead to falsely low HbA1c results
• Hemoglobin variants: Certain hemoglobin variants may interfere with HbA1c measurement
• Vitamin B12 or folate deficiency: These deficiencies can lead to falsely elevated HbA1c levels
• Kidney disease: Advanced kidney disease can affect HbA1c formation and measurement
• Pregnancy: HbA1c levels may be lower during pregnancy due to increased red blood cell turnover

Healthcare providers must consider these factors when interpreting HbA1c results, especially in patients with known comorbidities or unusual clinical presentations.

The Impact of HbA1c on Diabetes Complications

Maintaining good glycemic control, as reflected by HbA1c levels, is crucial for preventing or delaying diabetes-related complications. How does elevated HbA1c contribute to diabetic complications? Persistently high blood glucose levels, indicated by elevated HbA1c, can damage blood vessels and nerves throughout the body.

Complications Associated with Poor Glycemic Control

• Cardiovascular disease: Increased risk of heart attack, stroke, and heart failure
• Nephropathy: Progressive kidney damage leading to kidney failure
• Retinopathy: Damage to the retina that can cause vision loss or blindness
• Neuropathy: Nerve damage resulting in pain, numbness, or weakness, particularly in the extremities
• Peripheral vascular disease: Reduced blood flow to the limbs, potentially leading to amputation
• Increased susceptibility to infections
• Impaired wound healing

By maintaining HbA1c levels within target ranges, patients can significantly reduce their risk of developing these serious complications.

Point-of-Care HbA1c Testing: Revolutionizing Diabetes Management

The advent of point-of-care (POC) HbA1c testing has transformed diabetes management by providing rapid, on-site results. This technology allows healthcare providers to make immediate treatment decisions and adjustments, improving patient care and outcomes.

Benefits of Point-of-Care HbA1c Testing

• Immediate results: Allows for real-time treatment adjustments
• Improved patient satisfaction: Reduces the need for follow-up appointments
• Enhanced diabetes control: Studies show POC testing often leads to better glycemic control
• Cost-effective: Reduces laboratory costs and improves efficiency
• Increased patient engagement: Immediate feedback can motivate patients to improve self-management

While most studies support the benefits of POC HbA1c testing, it’s important to note that the accuracy and reliability of these devices can vary. Healthcare providers should ensure that POC devices are properly calibrated and validated against laboratory methods.

Strategies for Improving HbA1c Levels

For individuals with elevated HbA1c levels, implementing strategies to improve glycemic control is essential. What are effective ways to lower HbA1c? A combination of lifestyle modifications and medical interventions can help bring HbA1c levels into the target range.

Lifestyle Modifications

• Dietary changes: Adopting a balanced, low-glycemic diet
• Regular physical activity: Aim for at least 150 minutes of moderate-intensity exercise per week
• Weight management: Losing excess weight can significantly improve insulin sensitivity
• Stress reduction: Chronic stress can negatively impact blood glucose levels
• Consistent sleep patterns: Poor sleep can affect glucose metabolism

Medical Interventions

• Oral medications: Various classes of drugs can help manage blood glucose levels
• Insulin therapy: For those with type 1 diabetes or advanced type 2 diabetes
• Continuous glucose monitoring: Provides real-time glucose data to guide treatment decisions
• Regular check-ups: Frequent monitoring allows for timely adjustments to treatment plans

The most effective approach often involves a combination of these strategies, tailored to the individual’s needs and circumstances.

The Future of HbA1c Testing and Diabetes Management

As our understanding of diabetes and glycemic control evolves, so too does the technology and methodology surrounding HbA1c testing and interpretation. What advancements can we expect in HbA1c testing and diabetes management?

Emerging Technologies and Approaches

• Artificial intelligence: AI algorithms may help predict HbA1c trends and optimize treatment plans
• Continuous glucose monitoring integration: Combining CGM data with HbA1c for a more comprehensive view of glycemic control
• Personalized medicine: Tailoring HbA1c targets and treatment strategies based on individual genetic and metabolic profiles
• Novel biomarkers: Identifying additional markers that complement HbA1c in assessing long-term glucose control
• Improved point-of-care devices: Developing more accurate and user-friendly POC HbA1c testing options

These advancements promise to enhance our ability to manage diabetes effectively, potentially reducing the burden of complications and improving quality of life for individuals living with diabetes.

Conclusion: The Enduring Importance of HbA1c in Diabetes Care

Glycosylated hemoglobin, or HbA1c, remains a cornerstone of diabetes diagnosis, management, and research. Its ability to provide a long-term view of glycemic control makes it an invaluable tool for healthcare providers and patients alike. As we continue to refine our understanding of diabetes and develop new technologies, the role of HbA1c is likely to evolve, potentially becoming even more integral to personalized diabetes care.

By maintaining awareness of HbA1c levels and working to keep them within target ranges, individuals with diabetes can significantly reduce their risk of complications and improve their overall health outcomes. As research progresses, we can look forward to even more sophisticated and tailored approaches to diabetes management, with HbA1c continuing to play a central role in guiding treatment decisions and monitoring progress.

The journey from the initial discovery of glycosylated hemoglobin to its current status as a key diabetes biomarker exemplifies the power of scientific research in improving patient care. As we look to the future, the ongoing refinement of HbA1c testing and interpretation promises to further enhance our ability to manage diabetes effectively, offering hope for better outcomes and improved quality of life for millions of people worldwide.

Glycosylated hemoglobin – wikidoc

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]

Overview

Glycosylated (or glycated) hemoglobin (hemoglobin A1c, Hb_1c , or Hb_A1c) is a form of hemoglobin used primarily to identify the average plasma glucose concentration over prolonged periods of time. Its name is sometimes abbreviated to A1C. It is formed in a non-enzymatic pathway by hemoglobin’s normal exposure to high plasma levels of glucose. Glycosylation of hemoglobin has been implicated in nephropathy and retinopathy in diabetes mellitus. Monitoring the Hb_A1c in type-1 diabetic patients may improve treatment.^[1]

Historical Perspective

Hemoglobin A1c was first separated from other forms of hemoglobin by Huisman and Meyering in 1958 using a chromatographic column.^[2] It was first characterized as a glycoprotein by Bookchin and Gallop in 1968. ^[3] Its increase in diabetes was first described in 1969 by Samuel Rahbar and coworkers^[4] The reactions leading to its formation were characterized by Bunn and his co-workers in 1975.^[5]
The use of hemoglobin A1c for monitoring the degree of control of glucose metabolism in diabetic patients was proposed in 1976 by Koenig and coworkers.^[6]

Pathophysiology

In the normal 120-day life span of the red blood cell, glucose molecules join hemoglobin, forming glycated hemoglobin. In individuals with poorly controlled diabetes, increases in the quantities of these glycated hemoglobins are noted. Once a hemoglobin molecule is glycated, it remains that way. A buildup of glycated hemoglobin within the red cell reflects the average level of glucose to which the cell has been exposed during its life cycle. Measuring glycated hemoglobin assesses the effectiveness of therapy by monitoring long-term serum glucose regulation. The Hb_A1c level is proportional to average blood glucose concentration over the previous four weeks to three months. Some researchers state that the major proportion of its value is related to a rather short term period of two to four weeks.^[7]

Point-of-care measurement

The benefits of point-of-care testing have been reviewed^[8].

Most^{[9][10][11][12]}, but not all^[13] studies find that point-of-care testing improves diabetic control.

Point-of-care testing improves patient satisfaction^[14].

Point-of-care testing is calculated to be cost-effective^[15].

Interpretation of Results

Laboratory results may differ depending on the analytical technique, the age of the subject, and biological variation among individuals. Two individuals with the same average blood sugar can have A1C values that differ by as much as 1 percentage point.^[16] In general, the reference range (that found in healthy persons), is about 4%–5.9%.^[17]

Higher levels of Hb_A1c are found in people with persistently elevated blood sugar, as in diabetes mellitus. While diabetic patient treatment goals vary, many include a target range of Hb_A1c values. A diabetic person with good glucose control has a Hb_A1c level that is close to or within the reference range. The International Diabetes Federation and American College of Endocrinology recommend Hb_A1c values below 6.5%, while American Diabetes Association recommends that the Hb_A1c be below 7.0% for most patients. A high Hb_A1c represents poor glucose control. Persistent elevations in blood sugar (and therefore Hb_A1c) increase the risk for the long-term vascular complications of diabetes such as coronary disease, heart attack, stroke, heart failure, kidney failure, blindness, erectile dysfunction, neuropathy (loss of sensation, especially in the feet), gangrene, and gastroparesis (slowed emptying of the stomach). Poor blood glucose control also increases the risk of short-term complications of surgery such as poor wound healing.

Lower than expected levels of Hb_A1c can be seen in people with shortened red blood cell life span, such as with glucose-6-phosphate dehydrogenase deficiency, sickle-cell disease, or any other condition causing premature red blood cell death. Conversely, higher than expected levels can be seen in people with a longer red blood cell life span, such as with Vitamin B12 or folate deficiency.

The approximate mapping between Hb_A1c values and average blood glucose measurements over the previous 4-12 weeks is shown in the table.^[18]

Indications

Glycosylated hemoglobin is recommended for both

• Checking blood sugar control in people who might be pre-diabetic and
• Monitoring blood sugar control in patients with more elevated levels, termed diabetes mellitus.

For a single blood sample, it provides far more diagnostic information regarding glycemic behavior than a fasting blood sugar value. That being said, fasting blood sugar tests are crucial in making treatment decisions. The American Diabetes Association guidelines are similar to others in advising that the glycosylated hemoglobin test be performed at least two times a year in patients with diabetes who are meeting treatment goals (and who have stable glycemic control) and quarterly in patients with diabetes whose therapy has changed or who are not meeting glycemic goals.^[19]

Limitations

Changes in Diet and Treatment

Glycosylated hemoglobin measurement is not appropriate where there has been a change in diet or treatment within 6 weeks.

Abnormalities in Hemoglobin and Red Blood Cell Production

Likewise the test assumes a normal red blood cell aging process and mix of hemoglobin subtypes (predominantly HbA in normal adults). Hence people with recent blood loss or hemolytic anemia, or genetic differences in the hemoglobin molecule (hemoglobinopathy) such as sickle cell disease and other conditions are not suitable for this test. The alternative fructosamine test may be used in these circumstances and it similarly reflects an average of blood glucose levels over the preceding 2 to 3 weeks.

Variability Across Laboratories

There is variation among laboratories and a lack of consensus on a diagnostic threshold for glycosolated hemoglobin. For these and other reasons, no medical organization recommends the use of this test alone to diagnose diabetes. Instead, fasting plasma glucose or an oral glucose tolerance test are used.

Related Chapters

• Diabetes mellitus
• Hemoglobin

External links

• National Diabetes Information Clearinghouse
• Hemoglobin A1c Test

References

1. ↑ Larsen ML, Hørder M, Mogensen EF (1990). “Effect of long-term monitoring of glycosylated hemoglobin levels in insulin-dependent diabetes mellitus”. N. Engl. J. Med. 323 (15): 1021–5. PMID 2215560.CS1 maint: Multiple names: authors list (link)
2. ↑ Huisman TH, Martis EA, Dozy A (1958). “Chromatography of hemoglobin types on carboxymethylcellulose”. J. Lab. Clin. Med. 52 (2): 312–27. PMID 13564011.CS1 maint: Multiple names: authors list (link)
3. ↑ Bookchin RM, Gallop PM (1968). “Structure of hemoglobin A1c: nature of the N-terminal beta chain blocking group”. Biochem. Biophys. Res. Commun. 32 (1): 86–93. doi:10.1016/0006-291X(68)90430-0. PMID 4874776.
4. ↑ Rahbar S, Blumenfeld O, Ranney HM (1969). “Studies of an unusual hemoglobin in patients with diabetes mellitus”. Biochem. Biophys. Res. Commun. 36 (5): 838–43. doi:10.1016/0006-291X(69)90685-8. PMID 5808299.CS1 maint: Multiple names: authors list (link)
5. ↑ Bunn HF, Haney DN, Gabbay KH, Gallop PM (1975). “Further identification of the nature and linkage of the carbohydrate in hemoglobin A1c”. Biochem. Biophys. Res. Commun. 67 (1): 103–9. doi:10.1016/0006-291X(75)90289-2. PMID 1201013.CS1 maint: Multiple names: authors list (link)
6. ↑ Koenig RJ, Peterson CM, Jones RL, Saudek C, Lehrman M, Cerami A (1976). “Correlation of glucose regulation and hemoglobin AIc in diabetes mellitus”. N. Engl. J. Med. 295 (8): 417–20. PMID 934240.CS1 maint: Multiple names: authors list (link)
7. ↑ “Hemoglobin A1c Fact Sheet”. Michigan Diabetes Research & Training Center. Retrieved 2007-12-26.
8. ↑ Schnell O, Crocker JB, Weng J (2017). “Impact of HbA1c Testing at Point of Care on Diabetes Management”. J Diabetes Sci Technol. 11 (3): 611–617. doi:10.1177/1932296816678263. PMC 5505423. PMID 27898388.CS1 maint: Multiple names: authors list (link)
9. ↑ Cagliero E, Levina EV, Nathan DM (1999). “Immediate feedback of HbA1c levels improves glycemic control in type 1 and insulin-treated type 2 diabetic patients”. Diabetes Care. 22 (11): 1785–9. doi:10.2337/diacare.22.11.1785. PMID 10546008.CS1 maint: Multiple names: authors list (link)
10. ↑ Miller CD, Barnes CS, Phillips LS, Ziemer DC, Gallina DL, Cook CB; et al. (2003). “Rapid A1c availability improves clinical decision-making in an urban primary care clinic”. Diabetes Care. 26 (4): 1158–63. doi:10.2337/diacare.26.4.1158. PMID 12663590.CS1 maint: Multiple names: authors list (link)
11. ↑ Egbunike V, Gerard S (2013). “The impact of point-of-care A1C testing on provider compliance and A1C levels in a primary setting”. Diabetes Educ. 39 (1): 66–73. doi:10.1177/0145721712465340. PMID 23150529.
12. ↑ Petersen JR, Finley JB, Okorodudu AO, Mohammad AA, Grady JJ, Bajaj M (2007). “Effect of point-of-care on maintenance of glycemic control as measured by A1C”. Diabetes Care. 30 (3): 713–5. doi:10.2337/dc06-1909. PMID 17327346.CS1 maint: Multiple names: authors list (link)
13. ↑ Khunti K, Stone MA, Burden AC, Turner D, Raymond NT, Burden M; et al. (2006). “Randomised controlled trial of near-patient testing for glycated haemoglobin in people with type 2 diabetes mellitus”. Br J Gen Pract. 56 (528): 511–7. PMC 1872061. PMID 16834877.CS1 maint: Multiple names: authors list (link)
14. ↑ Laurence CO, Gialamas A, Bubner T, Yelland L, Willson K, Ryan P; et al. (2010). “Patient satisfaction with point-of-care testing in general practice”. Br J Gen Pract. 60 (572): e98–104. doi:10.3399/bjgp10X483508. PMC 2828863. PMID 20202351.CS1 maint: Multiple names: authors list (link)
15. ↑ Chadee A, Blackhouse G, Goeree R (2014). “Point-of-Care Hemoglobin A1c Testing: A Budget Impact Analysis”. Ont Health Technol Assess Ser. 14 (9): 1–23. PMC 4549575. PMID 26316923.CS1 maint: Multiple names: authors list (link)
16. ↑ Rohlfing C, Wiedmeyer HM, Little R; et al. (2002). “Biological variation of glycohemoglobin”. Clin. Chem. 48 (7): 1116–8. PMID 12089188.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
17. ↑ “Hemoglobin A1c Test”. MedicineNet.com. Retrieved 2007-12-26.
18. ↑ Bartol T (December 1, 2000). “Comparison of Blood Glucose, HbA1c, and Fructosamine”. Retrieved 2007-06-04. – gives a comparison chart and cites following source:
    • Nathan DM, Singer DE, Hurxthal K, Goodson JD (1984). “The clinical information value of the glycosylated hemoglobin assay”. N. Engl. J. Med. 310 (6): 341–6. PMID 6690962.CS1 maint: Multiple names: authors list (link)
19. ↑ American Diabetes Association (2007). “Standards of medical care in diabetes–2007”. Diabetes Care. 30 (Suppl 1): S4–S41. doi:10.2337/dc07-S004. PMID 17192377.

de:HbA1c
ko:당화혈색소
he:המוגלובין מסוכרר
hu:HbA1c
nn:Hemoglobin A1c
sv:Glykosylerat hemoglobin

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Glycated haemoglobin (HbA1c) for the diagnosis of diabetes – Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus

Recommendation

HbA1c can be used as a diagnostic test for diabetes providing that stringent quality assurance tests are in place and assays are standardised to criteria aligned to the international reference values, and there are no conditions present which preclude its accurate measurement.

An HbA1c of 6.5% is recommended as the cut point for diagnosing diabetes. A value of less than 6.5% does not exclude diabetes diagnosed using glucose tests.

Quality of evidence assessed by GRADE: moderate

Strength of recommendation based on GRADE criteria: conditional

Glycated haemoglobin (HbA1c) was initially identified as an “unusual” haemoglobin in patients with diabetes over 40 years ago (12). After that discovery, numerous small studies were conducted correlating it to glucose measurements resulting in the idea that HbA1c could be used as an objective measure of glycaemic control. The A1C-Derived Average Glucose (ADAG) study included 643 participants representing a range of A1C levels. It established a validated relationship between A1C and average glucose across a range of diabetes types and patient populations (13). HbA1c was introduced into clinical use in the 1980s and subsequently has become a cornerstone of clinical practice (14).

HbA1c reflects average plasma glucose over the previous eight to 12 weeks (15). It can be performed at any time of the day and does not require any special preparation such as fasting. These properties have made it the preferred test for assessing glycaemic control in people with diabetes. More recently, there has been substantial interest in using it as a diagnostic test for diabetes and as a screening test for persons at high risk of diabetes (16).

Owing in large part to the inconvenience of measuring fasting plasma glucose levels or performing an OGTT, and day-to-day variability in glucose, an alternative to glucose measurements for the diagnosis of diabetes has long been sought. HbA1c has now been recommended by an International Committee and by the ADA as a means to diagnose diabetes (16). Although it gives equal or almost equal sensitivity and specificity to a fasting or post-load glucose measurement as a predictor of prevalent retinopathy (17), it is not available in many parts of the world. Also, many people identified as having diabetes based on HbA1c will not have diabetes by direct glucose measurement and vice versa.

The relationship between HbA1c and prevalent retinopathy is similar to that of plasma glucose, whether glucose and HbA1c are plotted in deciles (18), in vigintiles () or as continuous variables (). This relationship was originally reported in the Pima Indians (19) and has also been observed in several other populations including Egyptians (20), the NHANES study in the USA (21),, in Japanese (22) and more recently in the DETECT-2 analysis ( and ). Overall, the performance of HbA1c has been similar to that of fasting or 2-h plasma glucose. For all three measures of glycaemia, the value above which the prevalence of retinopathy begins to rise rapidly has differed to some extent between studies. Although HbA1c gives equal or almost equal sensitivity and specificity to glucose measurement as a predictor of prevalent retinopathy, it is not available in many parts of the world and in general, it is not known which is the better for predicting microvascular complications.

Figure 1

Prevalence of diabetes-specific retinopathy (≥ moderate non proliferative retinopathy) by vigintiles of distribution of FPG, 2-h PG and HbA1c from DETECT-2.

Figure 2

Prevalence of retinopathy by 0.5 mmol/L intervals for FPG and 2-h PG and by 0.5% intervals for HbA1c for any retinopathy and diabetes-specific retinopathy (≥ moderate NPDR) from DETECT-2.

It is unclear whether HbA1c or blood glucose is better for predicting the development of retinopathy, but a recent report from Australia has shown that a model including HbA1c for predicting incident retinopathy is as good as or possibly better than one including fasting plasma glucose (23).

The use of HbA1c can avoid the problem of day-to-day variability of glucose values, and importantly it avoids the need for the person to fast and to have preceding dietary preparations. These advantages have implications for early identification and treatment which have been strongly advocated in recent years.

However, HbA1c may be affected by a variety of genetic, haematologic and illness-related factors (Annex 1) (24). The most common important factors worldwide affecting HbA1c levels are haemoglobinopathies (depending on the assay employed), certain anaemias, and disorders associated with accelerated red cell turnover such as malaria (16;25).

The utility and convenience of HbA1c compared with measures of plasma glucose for the diagnosis of diabetes needs to be balanced against the fact that it is unavailable in many countries, despite being a recognized valuable tool in diabetes management. In addition the HbA1c assay is not currently well enough standardized in many countries for its use to be recommended universally at this time. However, there will be countries where optimal circumstances already exist for its use. Factors influencing HbA1c assays are presented in Annex 2 and 3.

There are aspects of the measurement of HbA1c that are problematic. Although in some laboratories the precision of HbA1c measurement is similar to that of plasma glucose, global consistency with both assays remains a problem (16). Whether it is the glucose or HbA1c assay that is used, consistent and comparable data that meet international standards are required. This is starting to happen in many countries but obviously is still not standard across the world. Within any country, it is axiomatic that results for glucose and HbA1c should be consistent between laboratories.

The National Glycohemoglobin Standardization Program (NGSP) (26) was established following the completion of the Diabetes Complications and Control Trial (DCCT). For many years it was the sole basis for improved harmonization of HbA1c assays. More recently the International Federation of Clinical Chemists (IFCC) established a working group on HbA1c in an attempt to introduce an international standardization program (27). An important part of this effort was establishment of reference method procedures for HbA1c. Currently, both the NGSP and the IFCC base their evaluations on reference method procedures that have further enhanced the harmonization of HbA1c assays across manufacturers. Finally in the USA, the College of American Pathologists (CAP) has mandated more stringent criteria for individual assays to match assigned values for materials provided in the CAP proficiency programme (28).

A further major factor concerns costs and availability of HbA1c assays in many countries. Also, the situation in several of these countries will be exacerbated by high prevalences of conditions such as haemoglobinopathies, which affect HbA1c measurement, as discussed earlier.

A report published in 2009 by an International Expert Committee on the role of HbA1c in the diagnosis of diabetes recommended that HbA1c can be used to diagnose diabetes and that the diagnosis can be made if the HbA1c level is ≥6.5%(16). Diagnosis should be confirmed with a repeat HbA1c test, unless clinical symptoms and plasma glucose levels >11.1mmol/l (200 mg/dl) are present in which case further testing is not required. Levels of HbA1c just below 6.5% may indicate the presence of intermediate hyperglycaemia. The precise lower cut-off point for this has yet to be defined, although the ADA has suggested 5.7 – 6.4% as the high risk range (29). While recognizing the continuum of risk that may be captured by the HbA1c assay, the International Expert Committee recommended that persons with a HbA1c level between 6. 0 and 6.5% were at particularly high risk and might be considered for diabetes prevention interventions.

The WHO consultation reviewed the evidence on the relationship between HbA1c and prevalent and incident microvascular complications presented in the systematic review. and show HbA1c and glucose cut-off points associated with prevalent and incident microvascular complications in available studies. GRADE tables of evidence are presented in and . In view of the above and of the advances in technology over recent years, members of the consultation agreed that HbA1c may be used to diagnose diabetes providing that appropriate conditions apply, i.e. standardized assay, low coefficient of variability, and calibration against IFCC standards. Furthermore, each country should decide whether it is appropriate for its own circumstances. The choice of diagnostic method will depend on local considerations such as cost, availability of equipment, population characteristics, presence of a national quality assurance system etc. Policy-makers are advised to ensure that accurate blood glucose measurement be generally available at the primary health care level, before introducing HbA1c measurement as a diagnostic test. The consultation concluded that there is insufficient evidence to make any formal recommendation on the interpretation of HbA1c levels below 6.5%.

Table 1

HbA1c, FPG and 2-h PG cut-points associated with prevalent microvascular complications.

Table 2

HbA1c and FPG cut-points associated with incident diabetes complications.

Table 3

GRADE table for HbA1c and detection of prevalent microvascular complications.

Table 4

GRADE table for HbA1c and incident microvascular complications.

Long term prospective studies are required in all major ethnic groups to establish more precisely the glucose and HbA1c levels predictive of microvascular and macrovascular complications. A working group should be established to examine all aspects of HbA1c and glucose measurement methodology.

The diagnosis of diabetes in an asymptomatic person should not be made on the basis of a single abnormal plasma glucose or HbA1c value. At least one additional HbA1c or plasma glucose test result with a value in the diabetic range is required, either fasting, from a random (casual) sample, or from the oral glucose tolerance test (OGTT). The diagnosis should be made by the best technology available, avoiding blood glucose monitoring meters and single-use HbA1c test kits (except where this is the only option available or where there is a stringent quality assurance programme in place).

It is advisable to use one test or the other but if both glucose and HbA1c are measured and both are “diagnostic” then the diagnosis is made. If one only is abnormal then a further abnormal test result, using the same method, is required to confirm the diagnosis.

More and more asymptomatic subjects are being detected as a result of screening programmes so that diagnostic certainty is paramount. If such tests fail to confirm the diagnosis of diabetes, it will usually be advisable to maintain surveillance with periodic re–testing until the glycaemic status becomes clear.

Glycated hemoglobin – what is this analysis and why is it needed? –

It is also glycosylated hemoglobin, abbreviated as HbA1c.

Hemoglobin is a substance found in erythrocytes – blood cells – and is responsible for carrying oxygen from the lungs to all cells of the body. Many substances are dissolved in the blood plasma, including glucose (its content is shown by a blood test for sugar). A small part of glucose reacts with hemoglobin, joining it – this is how glycated hemoglobin is formed. This process is irreversible, goes without the participation of enzymes, the amount of glycated hemoglobin formed depends only on the concentration of glucose in the blood. Erythrocytes in the blood live on average for about 2-3 months. Thus, according to the content of glycated hemoglobin, one can fairly accurately judge the level of sugar in the blood in the previous 2-3 months.

Why check glycated hemoglobin when you can just measure blood sugar?

Blood sugar is not a constant value, it changes all the time. In the morning after an overnight fast, blood sugar is low, after eating it rises sharply, then gradually decreases. By determining fasting blood sugar, we only know sugar at a particular moment, but we do not know anything about its daily fluctuations. In patients with diabetes mellitus with poorly selected therapy or with a gross violation of the diet, blood sugar can change by 15-20 mmol / l during the day!

The level of glycated hemoglobin reflects all these sugar fluctuations. If a patient with diabetes rarely measures his blood sugar, then the level of glycated hemoglobin, the doctor can judge how high the average sugar level in this person was in the last 2-3 months. Often, a blood test for glycated hemoglobin helps the doctor decide whether to change the treatment regimen for a patient with diabetes.

A blood test for glycated hemoglobin is important in diagnosing diabetes mellitus. At the beginning of the disease, it often happens that fasting blood sugar remains within the normal range, but sugar after eating rises significantly, which the person does not know about. An elevated level of glycated hemoglobin in this situation will tell the doctor that an additional examination should be prescribed and help identify the disease.

Who needs a blood test for glycated hemoglobin?

• Patients with diabetes 1 time in 3 months
• Pregnant women diagnosed with diabetes during pregnancy
• Obese people, especially in combination with high blood pressure, high cholesterol, heart disease, diabetes in immediate family .
• Women with polycystic ovary syndrome,
• If a slightly elevated blood sugar (above 6.0 mmol/l) is found in the tests.

How to understand the results of the analysis?

The normal value of glycated hemoglobin is 4-6%.

A reading of 6.5% or more means you are more likely to have diabetes. To make a diagnosis, you need to take blood tests for fasting sugar and after eating.

6.0-6.5% – typical for prediabetes, in this case it is better to conduct an additional examination – a sugar curve.

There are a number of situations where a blood test for glycated hemoglobin is not informative. This happens with anemia of various origins, after blood transfusions. In the onset of type 1 diabetes, sometimes developing very quickly, glycated hemoglobin does not have time to rise despite a very high blood sugar level.

For patients with diabetes glycated hemoglobin norms are different. The target value is determined individually by the attending physician, it depends on the age of the patient, the presence of severe complications of diabetes. Most people with diabetes are advised to keep their glycated hemoglobin below 7.0%. For young patients without severe complications and without severe hypoglycemia, stricter control is recommended – glycated hemoglobin is not higher than 6. 5%. For elderly patients, patients with severe complications of diabetes or severe comorbidities, the target level is considered to be 7.5%.

Reception by:

Diabetologist – endocrinologist

Olga Vladimirovna Malakhova

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Blood test for glycated hemoglobin in Kiev

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Study code:
221

Unit:
%

Execution time:
1-3 working days

Material:
whole blood

Price:

230
UAH

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by price:
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Preparation

A mandatory requirement is the regime of complete refusal of food on the day of blood donation for analysis (in the evening of the previous day, a light dinner is recommended). When donating venous blood, it is necessary to exclude factors that affect the results of the research: physical stress (running, climbing stairs), emotional arousal. Therefore, before the procedure, you should rest for 10-15 minutes in the waiting room, calm down. You should not donate blood after exposure to X-rays (“X-rays”), physiotherapy procedures. Taking into account the daily rhythms of changes in blood parameters, it is advisable to take samples for repeated studies at the same time .

Research is accepted until 11.00 from Monday to Saturday, in all branches of the Dneprolab CLD in Kyiv.

Description

Glycated hemoglobin, or glycohemoglobin (abbreviated as hemoglobin A1c, HbA1c) is a biochemical blood indicator that reflects the average blood sugar over a long period (up to three months), in contrast to blood glucose measurement, which gives an idea of ​​the blood glucose level only at the time of the study.

Where can I take

Ukraine, Kiev, Vyshgorodskaya street, 21

st. Vyshgorodskaya, 21

Phones:

(044) 29-099-29

(093)929-09-929

viber (095) 29-099-29

Working hours:

Ukraine, Kiev, st. Popudrenko, 7

Popudrenko, 7

Phones:

(044)29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Brovary, st. Gagarina, 20b

Brovary, Gagarina, 20 B

Phones:

(044) 29-099-29

Viber (095) 29-099-29

Work schedule:

Ukraine, Kiev, Bazhana Avenue, 12

Bazhana Avenue, 12

Phones:

(044) 29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Kyiv, st. Petra Zaporozhets, 26

Petra Zaporozhets, 26

Phones:

(044) 29-099-29

(093)929-09-929

viber (095) 29-099-29

Working hours:

Ukraine, Cherkasy, 30th Anniversary of Victory 16/1

Cherkasy, 30th anniversary of the Victory 16/1

Phones:

(073)738-38-45

(044)29-099-29

Working hours:

Ukraine, Kiev, Mayakovskogo Avenue, 20

Mayakovskogo Avenue, 20

Phones:

(044) 29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Kyiv, st. Kurnatovsky, 7

Kurnatovsky, 7 (children’s department)

Phones:

(044) 29-099-29

(093)929-09-929

viber (095) 29-099-29

Working hours:

Ukraine, Kiev, st. Yakubovsky, 6

Yakubovsky, 6

Phones:

(044)29-099-29

viber (095)29-099-29

Working hours:

Ukraine, Kiev, 27 Geroev Stalingrad Ave

27 Geroev Stalingrad Ave

Phones:

(044)29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Kiev, st. Metropolitan Andrey Sheptytsky, 5

Sheptytsky (Lunacharsky), 5

Phones:

(044)29-099-29

viber (095)29-099-29

Working hours:

Ukraine, Fastov, st. L. Tolstoy, 28

Fastov, Tolstoy, 28

Phones:

(04565) 5-14-08

(044)29-099-29

Working hours:

Ukraine, Cherkasy, Chernovola 1

Cherkasy, Chernovola 1

Phones:

(073)056-59-27

(044)29-099-29

Working hours:

Ukraine, Kiev, st. Velyka Zhitomirskaya, 14

Velyka Zhitomirskaya, 14

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(044)29-099-29

viber (095)29-099-29

Working hours:

Ukraine, Kiev, Koltsov boulevard, 14Zh

Koltsov boulevard, 14Zh

Phones:

(044) 29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Kyiv, st. Dekabristov, 5

Dekabristov, 5

Phones:

(044) 29-099-29

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Working hours:

Ukraine, Kyiv, st. Kharkiv highway, 56

Kharkov highway, 56

Phones:

(044) 29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Sofievskaya Borshchagovka, st. Voloshkova, 30

Voloshkova, 30, Sofiyivska Borshchagovka

Phones:

(044) 29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Kiev, Trostyanetskaya, 8D

Trostyanetskaya, 8D (children’s nurse)

Phones:

(044)29-099-29

viber (095)29-099-29

Working hours:

Ukraine, Kyiv, st. Zakrevskogo, 42A

Zakrevskogo, 42A

Phones:

(044) 29-099-29

viber: (095)29-099-29

Working hours:

Ukraine, Chernihiv, Rokossovsky street, 49

Chernigov Rokossovsky, 49

Phones:

(044) 29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Kiev, ave. Pavel Tychyny, 3

Tychyny, 3

Phones:

(044)29-099-29

(095)29-099-29

Working hours:

Ukraine, Chernigov, Mazepy street, 4

Chernigov Mazepy, 4

Phones:

(044) 29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Fastov, Kommunalny lane, 7A

Fastov, Kommunalny lane, 7A

Phones:

(044)29-099-29

(095)29-099-29

Working hours:

Ukraine, Cherkasy, st. Baidy Vyshnevetsky 36/1

Cherkasy, st. Baidy Vyshnevetsky 36/1

Phones:

(073)750-16-08

(044)29-099-29

Working hours:

Ukraine, Kiev, Petra Zaporozhtsa, 26A

Petra Zaporozhtsa, 26A

Phones:

(044) 29-099-29

Viber (095) 29-099-29

Work schedule:

Ukraine, Kiev, Yaltinskaya street, 8

Yaltinskaya street, 8

Phones:

(044) 29-099-29

viber (095) 29-099-29

Working hours:

Ukraine, Kiev, st. Garmatnaya, 37A

Garmatnaya, 37A

Phones:

(044)29-099-29

viber (095)29-099-29

Working hours:

Ukraine, p.