HBA1C TEST: WHAT FACTORS AFFECT ITS RESULTS?

Several medical tests exist today. Usually, these tests are done to diagnose certain diseases. Other times, they are carried out as part of routine medical check-ups. The HbA1c test is one such medical test to monitor a condition.

As with most medical tests, it begins and ends with taking a blood sample which is then analyzed in a laboratory. But how important is it in monitoring one’s health status, and what can affect its results? We will discuss these and many more as you read further.

What Does HbA1c Mean?

“Hb” is an acronym for hemoglobin, a protein in red blood cells whose primary function is to carry oxygen inhaled around the body. HbA1 is the common variant of this protein present in healthy individuals. However, while transporting oxygen, hemoglobin could bind to excess glucose or sugar in the blood. This is when it becomes HbA1c which serves as a measure to measure A1c levels.

What Is the HbA1c Test?

Glycated hemoglobin test, glycohemoglobin test, and glycosylated hemoglobin test are all other names for the HbA1C test. It is a laboratory blood test that measures the average blood sugar level in the body over 2 to 3 months. Before being replaced, red blood cells have an average lifespan of four months. Hence the test is performed at these intervals. This helps diagnose diabetes and monitor it long-term.

The HbA1c test is carried out by a health professional who takes a blood sample from a vein in the arm using a small needle and then collects it in a test tube taken to the laboratory. The entire test’s duration is usually less than five minutes and does not require fasting or prior preparation.

Role of the HbA1c Test

When glucose from the food you take gets absorbed into the bloodstream and combines with hemoglobin, the process is called glycation. Now the rate of glycation is directly proportional to the glucose concentration in the blood. This means that if more glucose is in the blood, glycation increases, increasing the number of glycated hemoglobin molecules.

For the HbA1c test, analysis is done in the laboratory after a blood sample has been taken. A reagent is added to the sample to separate the glycated molecules from the normal ones. After this, a machine measures the hemoglobin molecules bound to glucose to report the A1c levels as a percentage.

Hemoglobin A1 and Hemoglobin A1c

Hemoglobin A1 is a normal hemoglobin component present in most healthy individuals. It is a combination of a protein component called globin and a sugar molecule called glucose. Hemoglobin A1c, on the other hand, is a subtype of the HbA1 formed when glucose molecules in the blood attach to hemoglobin itself.

It is the level of the HbA1c that forms the basis of the HbA1c test. Simply put, HbA1c is a normal component of hemoglobin, while HbA1c is an abnormal type of hemoglobin. The HbA1c test is also used to monitor blood glucose levels in people with diabetes since it serves as a measure, whereas the HbA1 does not serve this purpose. Hence, you cannot use these two interchangeably.

Normal HbA1c Levels

A healthy individual's average blood glucose level is usually below 5.7%, which signifies a normal blood sugar level. If the glucose levels are higher than normal, as in prediabetes, it ranges between 5.7 to 6.4%. For diabetes, the HbA1c level is always higher than 6.5%. Although, it is recommended that people with diabetes keep this level between 6.5 and 7 %, as anything higher could be dangerous.

Understanding HbA1c Test Result

As explained earlier, the normal level HbA1c percentage is 5.7%. The HbA1c percentage is the glucose that has been bound to the blood. In other words, it states the ratio of glycated hemoglobin in the blood to the total amount of hemoglobin present, which is then expressed as a percentage. A higher percentage connotes the blood sugar level is higher than usual, while a lower rate is vice versa.

However, this test is no substitute for standard blood glucose tests, which you can do as often as possible using a glucometer. The HbA1c test is designed for long-term control to help your doctor monitor your progress and, if need be, adjust your management plans.

Why Is Testing A1c Levels Important?

Here are a few reasons that attest to why A1c test measures are important:

• It helps diagnose diabetes early before it worsens, leading to other diabetes complications.
• It differentiates between type 1 and type 2 diabetes, which can be very similar in symptoms. However, this test alone is not enough for diagnosis. A fasting blood sugar or 2-hour glucose tolerance test can also be carried out. These tests should be taken on different days and have the results compared to diagnose correctly.
• It is also effective in helping to monitor the treatment plan for managing diabetes. Usually, the initial test is a baseline that should not be crossed during management. So its results can help patients know if they are improving or deteriorating.

Who Needs an HbA1c Test?

The HbA1c test is recommended by the Center for Disease Control (CDC) to test for prediabetes and diabetes if you are more than 45 years of age. In cases when the results are normal, you can repeat the test every three years, but if there are traces of prediabetes, every 1 or 2 years.

Also, this test is not only limited to individuals older than 45. As a younger adult, you should take this test if:

• you are overweight, or obesity is present
• you have an immediate relative (sibling or parent) diagnosed with type 2 diabetes
• your blood pressure and cholesterol levels are high
• you are mostly physically inactive on most days of the week
• your race is at risk
• you had diabetes while pregnant, or your child’s weight at birth was over 9 lbs
• you recently had a stroke or heart condition
• you have PCOS (Polycystic Ovarian Syndrome)
• you have more than two symptoms of diabetes at the same time

Factors Affecting HbA1c Test Results

Several risk factors or conditions affect the result of the HbA1c test when taken. A few of them are discussed below:

Pregnancy

Have you ever heard of gestational diabetes? It is merely a type of diabetes that happens during pregnancy and raises the possibility of the mother later having the disease. Hormonal changes during pregnancy alter insulin production, which leads to elevated blood sugar levels. This usually occurs during the second or third trimester, but after delivery, it goes away.

On the other hand, in other women, pregnancy results in a low blood sugar level, especially in the second trimester. So if the HbA1c test is taken on a pregnant woman, there is no telling if the results are accurate as pregnancy hormones could have altered the sugar level.

Recent or Heavy Blood Loss

If you recently lost a lot of blood or even some of it, it can also affect the result of the Hb1Ac test taken in that period. When one loses blood, the number of red blood cells in circulation is significantly reduced, and remember that hemoglobin is present in these cells.

So if the concentration of this protein in the blood has decreased, there will be few left for sugar to bind to, which means that the blood sugar level in that period will appear reduced. This means false lower HbA1c levels. If you recently lost blood, you should take more time for your body to produce new red blood cells before you take the test.

Recent Blood Transfusion

When blood gets transfused into the body, the new blood replenishes the red blood cells that have been lost. However, the downside is that the new blood might contain glycated hemoglobin molecules from the donor’s body.

So, the recipient will likely have red blood cells with different lifespans and glucose levels. Imagine testing a blood sample with varying cells containing different HbA1c levels; you might not get an accurate result from such a test.

Anemias and Iron Deficiency

A condition known as anemia results in a reduction in the number of hemoglobin or red blood cells in the blood. So when the amount of hemoglobin present for glycation is reduced, it lowers the HbA1c result even when the blood glucose levels over the past few months have been elevated. There are different types of anemia based on their causes, and they include:

• vitamin-deficiency anemia
• iron-deficiency anemia
• hemolytic anemia (red blood cells are destroyed faster than they are produced)
• aplastic anemia (bone-marrow not producing adequate blood cells)
• sickle cell anemia, thalassemia (production of abnormal hemoglobin) and
• anemia due to chronic diseases.

Iron is an essential component of hemoglobin, so if it is deficient in the body, it leads to iron-deficiency anemia. If there is an iron overload in the body, too, it could lead to a higher red blood cell count, which elevates the HbA1c test result even when the blood glucose levels are within the normal range.

All this means the amount of iron in the body, the presence or absence of a medical condition like anemia, and the HbA1c level in the body are interlinked. So these must be checked before the test to ensure an accurate result.

Hemoglobin Variants

There are different variants of hemoglobin. The variant you would have is usually inherited from a gene or trait in your biological parents. HbA is the most common form of hemoglobin. However, there are HbC, HbD, HbE, and HbS, which are present in people from different regions across the globe.

These hemoglobin variants do not increase your chances of elevated blood sugar levels but can affect your A1C test results. For instance, a standard test designed for the common HbA being done on blood containing the HbD reduces the chances of getting an accurate result. This is why there have been modifications in how the A1C test is carried out on other hemoglobin variants in a specialized laboratory to diagnose and monitor diabetes.

Kidney Failure

This serious medical condition results from one or both kidneys not functioning independently. One of the functions of the kidneys is to eliminate excess glucose from the blood. So when their functioning is impaired, there will be a buildup of glucose in the body, resulting in a higher HbA1C level.

This is why if an individual suffers from chronic kidney failure, it may not be the best time to carry out the HbA1c test as it is not a true reflection of their blood sugar levels. Note that even after a kidney transplant, there could still be an elevation in the blood glucose level due to the immunosuppressive medications that will be taken after the transplant.

Conclusion

The HbA1c provides a good picture of the average blood sugar levels over a few months, making it valuable for diagnosing and monitoring type 2 diabetes. However, certain factors could deter this test from giving accurate results.

This is why there is a need for a thorough assessment by the health professional before carrying out the test, so more harm than good is not done. You should also ask questions and report any changes since you did your last HbA1c level so you are provided with the right treatment plan.

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Sources:

• The A1C Test & Diabetes
• All About Your A1C
• Role of Glycated Proteins in the Diagnosis and Management of Diabetes: Research Gaps and Future Directions
• Hemoglobin and Hematocrit
• Significance of HbA1c Test in Diagnosis and Prognosis of Diabetic Patients
• Diabetes & Prediabetes Tests

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