What is HbA1c? It is simply the hemoglobin molecule in red cells that has had glucose (blood sugar) attached to it. Hemoglobin is the molecule responsible for the red appearance of blood and it is also vital to life because it transports oxygen to all of our tissues to sustain life. Many years ago it was noted that HbA1c levels, that is, hemoglobin with sugar in the form of glucose attached to it, were elevated in diabetics compared to the general population. Diabetes is a disease in which blood sugar (glucose) levels are chronically too high, leading to many problems, such as kidney failure and blindness.
Eventually, studies showed that HbA1c could be used as a monitor for blood sugar levels in diabetics and was less prone to day to day variation and laboratory handling problems than glucose testing, which of course had been the standard test for monitoring diabetics for many years. Measuring glucose in the lab can be a problem, because interpretation of results is dependent on whether you were fasting before the sample was taken and also because measurement of glucose itself is made difficult because red cells in sample tubes continue to utilize glucose for many hours after the sample is taken. In other words, those red cells are still alive and they want the glucose for energy production!
Turns out HbA1c is not only useful for diagnosis and monitoring of diabetes, but it is also an extremely effective death marker! In other words, your HbA1c level can predict your odds of dying even if you are not a diabetic! Let's examine some recent data (ref.1) which shows the power of HbA1c as a predictor of death (mortality). The following table shows your chance of dying based on your HbA1c level, with data for age less than (<) 55 and for age 55 and older (≥):
These types of results have not been dealt with before because HbA1c testing was almost exclusively used to monitor blood sugar control in diabetics. But since the test was approved for diagnosis of diabetes, it now means that many people who are not diabetic have received an HbA1c result. I imagine most people and their doctors breathe a sigh of relief when their HbA1c level is lower than 6.5%, which is the cutoff value used to diagnose diabetes, that is, if your HbA1c value is higher than 6.5% you will be diagnosed with diabetes. But is anyone paying attention if your HbA1c level is less than 5%? Does your doctor realize that your risk of death from any cause is elevated up to twofold if your value is less than 5%? Highly doubtful, since the American Diabetes Association states that a normal HbA1c level is 4-6% (ref.2).
What we can be sure of is that what we have in HbA1c is a cheap and accurate death marker, and a death marker with predictive value whether it is too high or too low!
How's that for precision medicine right under your nose!
1. Paprott R et al. Association Between Hemoglobin A1c and All-Cause Mortality: Results of the Mortality Follow-up of the German National Health Interview and Examination Survey 1998. Diabetes Care 38: 249-256, 2015.
2. American Diabetes Association: Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 2009 Jan;32:Sup 1
© 2016 Ralph Giorno