The diagnosis of diabetes has major ramifications for the family and child/adolescent and therefore must not be made without certainty. There are four ways to diagnose diabetes (all types including: type 1, type 2, type 1.5, gestational, permanent neonatal diabetes, MODY, steroid or medication induced diabetes, Cystic Fibrosis related diabetes, etc.). They are as follows:
- Fasting blood sugar on two occasions greater than 126 mg/dl.
- Random blood sugar greater than 200 mg/dl along with symptoms related to new onset diabetes including increased drinking, increased urination, increased appetite, and weight loss.
- Two hour oral glucose tolerance test (75 grams of carbohydrates): blood sugar greater than or equal to 200 mg/dl.
- Hb A1c greater than or equal to 6.5 percent (reflecting a 3-month estimated blood sugar average of 139.85 mg/dl.
Pre-diabetes (or impaired glucose tolerance) is diagnosed by the following criteria:
- Fasting blood sugar greater than 100 mg/dl and less than 126 mg/dl on two separate occasions.
- Two hour postprandial blood sugar (oral glucose tolerance test) greater than 140 mg/dl and less than 200 mg/dl.
- Hb A1c between 6.0 and 6.4 percent on two separate occasions.
There has been considerable discussion among the different endocrine organizations in regard to the hb A1c as a diagnostic tool; however, the American Diabetes Association has adapted it as the fourth way in which to diagnose diabetes. As I have mentioned previously, diagnosis of type 1 diabetes in children and adolescents is typically based on criteria number two above, but not always. In situations of uncertainty, especially in the possibility of type 2 or other forms of diabetes, I use several criteria to confirm the diagnosis.
A recent article in the Journal of Pediatrics posted online ahead of print,
"Diagnosis of Diabetes using Hemoglobin A1c: Should Recommendations in Adults Be Extrapolated to Adolescents?" (doi: 10.1016/j.jpeds.2010.11.026), is an epidemiologic study looking at the ability of the hb A1c to diagnose diabetes in the adolescent population. The authors Lee, Wu, Tarini, Herman and Yoon's objectives were to compare efficacy of hemoglobin A1c for detecting diabetes/pre-diabetes for adolescents versus adults in the United States. They choose individuals with criteria for the diagnosis of diabetes mentioned above as well as those with pre-diabetes. Fasting blood sugars were obtained in 1,156 obese and overweight adolescents from 12 to 18 years of age. The blood sugars were then compared to fasting blood sugars in 6,751 adults from 19 to 79. The authors also compared results of the two-hour oral glucose tolerance test in 267 adolescents and 1,476 adults.
The hb A1c test was evaluated statistically applying receiver operator characteristic (ROC) analyses. Sensitivity versus specificity in the diagnosis of diabetes also was evaluated. (Sensitivity refers to the proportion of people with the disease who have a POSITIVE test result. Specificity refers to the proportion of people without the disease who have a NEGATIVE test result).