Did you know that 1 in 11 Americans today has diabetes? Despite its prevalence, diabetes is an invisible disease. It affects men and women, people young and old, and people of all races, shapes and sizes. Often there are no outward signs from the 29 million Americans who fight this chronic illness every day. That’s why there is a critical need to foster awareness and education while breaking down stereotypes, myths and misunderstandings about this growing public health crisis that affects so many of us.
The clinical laboratory’s critical role in Diabetes monitoring
Blood sugar (glucose) monitoring is perhaps the most obvious way that lab testing matters to the diagnosis and ongoing care of diabetic patients. While “point-of-care” home glucose test strips do indeed help patients to better manage their disorder between medical appointments, physicians still rely on the clinical laboratory for a more detailed picture of a patient’s metabolic state.
November is American Diabetes Month, established by the American Diabetes Association as a way to bring attention to the tens of millions of Americans living with diabetes. Nearly 10% of Americans have diabetes, and this number is growing as the population ages. Obesity is also a known risk factor for developing diabetes, which means that the disorder also affects a large number of overweight young adults and teens. Once diagnosed, diabetic patients must learn to maintain a healthy blood sugar through exercise, diet, and medication.
Long-term high blood sugar (hyperglycemia) is associated with higher risk of complications of diabetes, so keeping track of a patient’s glycemic control is very important. Persistent hyperglycemia is correlated with kidney failure, peripheral vascular disease, retinopathy, and fatty liver disease. Regular laboratory testing allows for early detection and intervention and can help physicians to manage these complications if they arise.
Sugar over time
Glucose in the bloodstream crosses through red blood cell membranes and binds to the hemoglobin molecules inside. The result is a glycated compound called Hemoglobin A1c or HbA1c. Many people, patients, and laboratorians alike, are already familiar with this laboratory test and its use in the management of diabetes. Measurement of HbA1c is useful to clinicians because it is a stable molecule that stays locked inside red blood cells over the course of their four-month lifespan.
Point-of-care glucose testing can only provide snapshots of a patient’s blood sugar each time the test is done, and a record of those results can show wide variation. Daily, even hourly, fluctuations in glucose levels are normal. Blood sugar can be temporarily affected by exercise, diet, and stress, so the timing of a random glucose measurement can make a big difference in the numbers that are reported. HbA1c measurement is a way to assess a sort of average blood sugar over the previous two to three months, which can help a physician to understand how well a patient is managing their diabetes over the long term. In some practices, the HbA1c test is used along with fasting blood glucose as an initial screening test for diabetes.
One Assay Doesn’t Fit All
Using HbA1c levels to diagnose and monitor diabetic patients has limitations. There are several different assays for measuring HbA1c, with no single global standard. Glycated hemoglobin can be measured by immunoassay, enzymatic assay, high-performance liquid chromatography, or boronate affinity assay, and results can vary several percentage points between methods. This means that a patient who switches to a different medical provider and a different lab may see a sudden shift in their HbA1c results despite making no changes to their routine.
Additionally, conditions that alter the lifespan of red blood cells, like bleeding, blood transfusions, iron deficiency anemia, and hemolytic anemia, can significantly affect the HbA1c value. Physicians treating diabetic individuals with any of these complicating disorders need to be aware of the test’s possible limitations and investigate results that don’t make sense for their patients.
Different assay methods can also be affected by genetic mutations in the hemoglobin molecule, falsely lowering or elevating the result. The National Glycohemoglobin Standardization Program (NGSP) provides information for clinicians and laboratorians about how different assays may be affected by hemoglobin variants. Patients carrying a mutation for sickle cell trait, or who have persistent fetal hemoglobin, are likely to have laboratory HbA1c results that correlate poorly with their home glucose monitoring results.
Because of the variability between methods, especially for patients with bleeding disorders or abnormal hemoglobin genes, it’s important for labs to make it easy for clinicians to know which method of measurement is being used. In cases where the results don’t correspond with the clinical picture, a provider may need to find a lab that is using a different assay or use an alternative method of longer-term glucose monitoring.
This November, the American Diabetes Association will showcase real-life stories of friends, families and neighbors managing the day-to-day triumphs and challenges of diabetes. The 2016 campaign,sponsored by Colgate Total® (National Oral Care Strategic Partner) and Medtronic Diabetes®, invites all of us to use #ThisIsDiabetes to share personal stories and to start a dialogue about what it really means to live with diabetes.