Today I had the opportunity to review posts from fellow bloggers on this site. Natalie's blog "A1c is not enough" specifically caught my attention as she noted that her diabetes would not have been diagnosed simply by a hb A1c initially but rather by review of fasting and post-prandial blood sugars. As such, I would like to review the criteria currently used to diagnose diabetes (all types, except gestational diabetes, which has different criteria).
- Fasting blood sugar > 126 mg/dl on two separate occasions.
- Random blood sugar > 200 mg/dl along with symptoms associated with diabetes including increased urination, increased drinking, increased appetite, fatigue, weight loss, etc. (These criteria are typical of those children/teens/adults who are diagnosed with type 1 or insulin dependant diabetes.)
- Oral glucose tolerance test (75 grams of anhydrous carbohydrates) with a 1-2 hour post prandial blood sugar > 200 mg/dl.
- Hb A1c >/= 6.5% (newest diagnostic criteria and still controversial). A hb A1c of 6.5 reflects a 3-month estimated blood sugar of 138.85 mg/dl in people that glycate the hemoglobin molecule normally. The hb A1c reflects the binding (or glycation) of the glucose molecule to the hemoglobin molecule that resides in the red blood cell. Due to the fact that red blood cells turn over approximately every 3 months, we are able to use the hb A1c to reflect blood sugar control every 3-4 months.
Generally, any one of these 4 criteria may be used to diagnose diabetes when reviewing the entire picture. However, one must be extraordinarily cautious when actually making the diagnosis definitively. Several cases in point:
- Diagnosis of diabetes by blood sugar alone:
a. High blood sugar, sick kid! A 5-year old presents to the local Emergency Department with a fever of 105 degrees in association with vomiting and lethargy. Laboratory evaluation reveals a very high white blood cell count indicating a suspected infection and a blood sugar of 362 mg/dl. The serum blood sugar is repeated and confirmed. When the mother is questioned further about associated symptoms of increased urination, increased drinking, etc., she is not sure but it could be possible. Does this child have diabetes? Maybe or maybe not. Further evaluation is necessary by the healthcare team to determine if, indeed, this child has newly diagnosed diabetes versus stress-induced hyperglycemia secondary to a significant infection! A hb A1c may help to confirm or rule out the diagnosis.
b. High blood sugar, child with asthma on prednisone: A 10-year old presents to the Emergency Department with wheezing after beginning Prednisone prescribed by his primary care practitioner several days ago. He is given nebulizer treatments and his blood sugar is noted to be 202 mg/dl. Does he/she have diabetes? Is the diagnosis new onset type 1 diabetes versus steroid induced hyperglycemia? Once again, a hb A1c may help to clarify the situation.