Lab Test Knowledge: HbA1C

What is HbA1C?

HbA1c is also known as glycosylated hemoglobin. Hemoglobin is a component of red blood cells that carries oxygen. When hemoglobin binds with glucose in the blood, HbA1c is formed. The higher the glucose concentration in blood, the higher the levels of HbA1c.

Red blood cells can survive for 8 to 12 weeks in our body. That's why the levels of HbA1c are not influenced by daily fluctuations in the blood glucose concentration, but reflect the average glucose levels over the last 6 to 8 weeks. Because HbA1c can be used to tell how well the blood glucose level has been controlled in the past, it's an important tool to track the progress of any diabetes management plan.

How to interpret the values?

a diabetes control card

• In non diabetic patients the normal HbA1c level is less than 7%. HbA1c levels over 6% is sufficient to identify people who are at an increased risk for diabetes.
• In people with diabetes, a HbA1c levels below 6.5% shows good diabetes control.
• For people who are at risk for getting hypoglycemia, a level of 7.5% is an acceptable target.

How often should you repeat measurement?  

If your diabetes is in good control, repeat HbA1c measurement every 6 month. If you are trying to improve control or if you are making changes in your treatment plan, repeat the test after 3 months. Repeating HbA1c test sooner than 6 weeks after the last measurement provides little or no information and is not cost effective.

What are the limitations of HbA1c?

Although HbA1c test is an important tool that tells how well you're doing over the past months, it can't replace daily blood glucose monitoring for those who need it. HbA1c levels can't be used to adjust insulin dosage, nor can it detects the presence of hyperglycemia or hypoglycemia.

In people with kidney disease, chronic excessive alcohol intake, and hypertriglyceridemia, HbA1c levels may be falsely increased. Blood loss either acute or chronic and several diseases of the red blood cells like thalassemia and sickle cell disease may falsely decreased HbA1c levels.

Screening Tests and Why They Are Important

Why screening tests are important

Screening tests helps to identify people with increased risk for a health disorder before they have symptoms or even realize they may be at risk. These laboratory tests are important because finding out early that you have or at risk to contract certain condition means you can take preventive measures.
 


Because a good screening test detects a disease in the earliest stages, it's most beneficial when you are tested for diseases that are both serious and treatable. A good screening must be able to correctly identify individuals who actually have a given disease, meaning that test is sensitive.

A positive screening test result often requires follow-up testing with a more specific test. This is to avoid 'false positive' in which a person without the given disease came out with a positive result.

"Screening tests are most beneficial to detect serious but treatable diseases."

Every year the U.S. Preventive Services Task Force (USPSTF) publish a guidelines that contains recommendations pertaining to whom and when should these screening tests be performed. Below are a few examples:

hypertension screening begins at 18 years old

• Screening for high blood pressure in adults aged 18 and older.
• Both men aged 35 and older and women aged 45 and older who are not at increased risk for coronary heart disease are to be screened for lipid disorder.
• If they are at increased risk for coronary heart disease, screening for lipid disorder should start early at age 20 to 35 for men and age 20 to 45 for women
• Screening mammography for breast cancer detection in women aged 50 to 74 years, to be repeated every two years. 
• Screening for colorectal cancer using fecal occult blood testing, sigmoidoscopy, or colonoscopy in adults begins at age 50 and continuing until age 75. 
• Women aged 65 and older to be screened routinely for osteoporosis. In women who are at increased risk screening begin at age 60.
• Screening for type 2 diabetes in otherwise healthy adult with sustained blood pressure (either treated or untreated) greater than 135/80 mm Hg.

Not every laboratory tests are necessary. Don't go ballistic and ask your physician to put a check next to every single test on the lab form. Instead discuss with your doctor which screening tests that are right for you taking consideration of your age, gender, and other risk factors like family history of cancer, unhealthy lifestyle, etc. Also there are diseases in which screening tests are unnecessary and ineffective, such as lung cancer, ovarian cancer, and pancreatic cancer.