I have been on service at Children's National Medical Center this past week. This means I am the physician that admits children and adolescents with new onset diabetes. As we are a tertiary children's hospital, many of our children are referred from great distances to both confirm the diagnosis and then treat accordingly. It is extremely important to be sure that the diagnosis of diabetes is appropriate before telling the family that their child/adolescent now has a chronic and incurable (as of now) illness. After this busy week where we had many children with both new onset type 1 and type 2 diabetes as well as children with high blood sugars that did not have diabetes, I wanted to take the opportunity to review the diagnosis of diabetes. In other words, how to distinguish between hyperglycemia caused by other reasons versus new onset diabetes.
Currently, there are four ways to diagnose diabetes (both type 1 and type 2):
1. Symptoms of increased urination, increased drinking, increased appetite and weight loss in association with a random blood sugar greater than 200 mg/dl.
2. Fasting blood sugars greater than 126 mg/dl on 2 separate occasions.
3. Oral glucose tolerance test (75 grams of carbohydrates) with resulting 2-hour post-prandial blood sugar greater than 200 mg/dl. (Note: different carb amounts are utilized for diagnosis of "gestational diabetes.")
4. Hb A1c greater than 6.5 percent (note that the hb A1c may not always be accurate in adolescents).
Pediatric healthcare teams usually see children/adolescents who present with the first cluster of symptoms and random blood sugars greater than 200 mg/dl. This is because the overwhelming majority of children are diagnosed with type 1 diabetes (Children's National statistics: 89 percent type 1 diabetes and 11 percent type 2 diabetes). Children and adolescents that present with either fasting blood sugars greater than 126 mg/dl or abnormal glucose tolerance tests often have type 2 diabetes although it is important to remember that children with type 2 diabetes can have symptoms identical to those with type 1. In our practice, the hb A1c is a useful adjunct to the diagnosis of diabetes but we do not totally rely on it as the definitive answer. The hb A1c is often very useful to distinguish between new onset diabetes and hyperglycemia from other reasons.
What are the situations in which hyperglycemia might occur in children and adolescents who do not have new onset diabetes?
1. Stress-induced hyperglycemia: These children are often very ill with an underlying condition. Examples include infections that cause a high fever, and those situations in which the body produces a burst of counter-regulatory hormones including adrenalin, cortisol, growth hormone and glucagon to "raise" blood glucose to fight the offending intruder. These children are often quite sick with concomitant high blood sugars. If we ask about the symptoms associated with diabetes, such as increased urination, families are often uncertain.
Therefore, to rule out diabetes, our practice is to obtain a "stat" hb A1c to help with the diagnosis. Clearly, if the hb A1c is under 6 percent, the diagnosis of diabetes is highly unlikely. Of course, the problem arises if the hb A1c is over 6 percent that could indicate evolving diabetes. We then must use clinical judgment.
2. Steroid/Medication induced hyperglycemia: In this situation, children have been given a medication that might induce high blood sugars such as steroids or chemotherapeutic agents. A typical scenario is that of a child/adolescent presenting to the Emergency Department with an asthma exacerbation that has been on Decadron (steroid) for the last 5 days and hyperglycemia is noted on the laboratory panel. Once again, we order a stat hb A1c to help distinguish, if indeed, the child has steroid induced hyperglycemia vs. new onset diabetes.
If the hb A1c is borderline in both cases noted above, we observe these children very carefully as outpatients and often have them test blood sugars with glucose meters to determine if they continue to have hyperglycemia when the acute illness is over and when the course of medication is over. If they continue to have intermittent hyperglycemia, we repeat fasting blood sugars and may repeat an oral glucose tolerance test as well as the hb A1c. The main issue is for the families to remain in close contact with either their primary care provider or diabetes team to observe for the potential development of type 1 or type 2 diabetes especially if impaired glucose tolerance is noted by fasting blood sugar (100-125 mg/dl) or oral glucose tolerance test (140-200 mg/dl 2 hours post prandial).
Clinical judgment is paramount whereby one relies not only on lab work but history of the illness, physical examination, and clinical course.