Dr. Roach: A1c is better screening test for diabetes
Dear Dr. Roach: My A1c test on blood sugar is always higher (prediabetes) than my fasting glucose test (normal) on the same visit to the doctor. Which result should I believe?
My latest test at a doctor’s office showed that my A1c is 6.2 percent, and fasting glucose is 88 mg/dL. The A1c pretty much remained at 6.2 percent level, while the fasting glucose varied between 81 and 88 in the past two years. The test is drawing a blood sample after a 12-hour overnight fast. I am not taking any diabetes medication. Previously, my A1c results were 5.9 percent in August 2016 and 5.5 percent in December 2016.
Dear K.H.: Both the A1c test and the glucose tests are blood tests for diabetes. The blood glucose test is a snapshot of an instant in time, while the A1c is a measure of the average value over the past two or three months or so. The A1c looks at the amount of sugar molecules on the large hemoglobin protein of the blood.
In general, the A1c is a better screening test for diabetes than a fasting glucose test, because fasting blood sugar is normal for a long time (potentially years) before one shows overt diabetes. In early Type 2 diabetes, the only time the blood sugar gets above normal is after eating (the blood sugar is supposed to go up a bit after eating, but in the early stages of diabetes, it goes higher than it should).
The most sensitive test for Type 2 diabetes is a glucose tolerance test, where a fixed amount of sugar is given, and the blood is tested after two hours. An elevated level at two hours is prediabetes or diabetes. However, the A1c, which is affected by both fasting blood glucose levels and those after eating, is nearly as sensitive, and is much easier to do. Both the glucose tolerance test and the A1c usually will diagnose prediabetes and diabetes before the fasting glucose becomes abnormal.
In your case, the A1c has been abnormal twice (less than 5.7 percent is normal, 5.7 percent to 6.5 percent is prediabetes and over 6.5 percent is diabetes), and your fasting blood sugar is normal, suggesting early prediabetes. Now is the time to make some changes in your diet and exercise regimen, if possible, and maybe lose a few pounds, as these can reduce the likelihood of developing overt diabetes. A registered dietary nutritionist can be an invaluable source of information on proper nutrition: It’s a lot more than just avoiding sweets.
Not everybody who develops Type 2 diabetes is overweight, doesn’t exercise properly or eats poorly. It’s possible to develop diabetes despite doing everything you can. However, nearly everybody can reduce their risk through lifestyle, and some will need medication.
Dear Dr. Roach: My husband never washes his hands. He handles vegetables after handling raw meat. I told him he is contaminating the foods, but he said that I am foolish and he will never wash his hands.
Dear T.: Raw meat is frequently contaminated by potentially harmful bacteria, such as E. coli, Salmonella and others. Cooking food thoroughly kills the bacteria, but vegetables are not usually heated enough to get rid of the bacteria, so he is continually exposing himself (and you) to potentially serious infection. Hands should be washed before and after handling meat, and meats and vegetables should be prepared using different cutlery and cutting boards.
Email questions to ToYourGoodHealth@med.cornell.edu.