Impaired Fasting Glucose: When and How to Intervene?

My 46-year-old patient had a fasting plasma glucose level of 115 mg/dL; a followupfasting plasma glucose level was 116 mg/dL. A year earlier, his fasting glucoselevel was 103 mg/dL and urinalysis results were negative. The patient is tall; hisbody mass index (BMI) is 25 kg/m² He has no significant medical history; however,his maternal grandmother and aunt both had type 2 diabetes.

The patient appears to have impaired glucose tolerance-although I havenot yet received the results of tests for glycosylated hemoglobin and microalbumin.Should I simply follow this patient with occasional fasting glucose levels, ordera glucose tolerance test, or begin treating him for diabetes?
-MD

This case raises at least 3 questions:

• Does the patient have diabetes mellitus?
  
• If so, which type?
  
• What treatment, if any, is require
  

Does the patient have diabetes?

The diagnosis of diabetes canbe made if 1 of the following 3 criteria is met:

• The fasting plasma glucose level is at least 126 mg/dL.
  
• The patient has symptoms of diabetes and a casual (measured at any time ofday) plasma glucose level of 200 mg/dL or above.
  
• The plasma glucose level is 200 mg/dL or greater 2 hours after administrationof a 75-g oral glucose dose.¹

Fasting plasma glucose levels of 115 mg/dL and 116 mg/dL do not meetthe diagnostic criteria for diabetes. Instead, patients with these values haveimpaired fasting glucose. Such patients are at high risk for later developmentof overt diabetes.

What type of diabetes would be most likely? A family history suchas this man's suggests type 2 diabetes. However, a BMI of 25 kg/m² and a relativelyslender body habitus raise the possibility of type 1 diabetes. Since wenow know that this disease can begin at any age, I suspect that type 1 diabeteswould eventually develop, necessitating insulin therapy.

Is treatment recommended?

The American Diabetes Association recommendsthe following treatment goals for all persons with diabetes:

• Preprandial blood glucose level between 80 and 120 mg/dL.
  
• Bedtime blood glucose level between 100 and 140 mg/dL.
  
• Hemoglobin A_1c less than 7% in an assay in which the upper limit of normalis 6%.²

I suspect that all values for a patient such as this man would be within thegoal ranges. Thus, I would not initiate treatment at this point. Rather, I wouldteach the patient how to monitor blood glucose levels at home and followclosely. An oral glucose tolerance test would not be useful.
-John P. Bantle, MD
  Professor of Medicine
  Division of Endocrinology and Diabetes
  University of Minnesota School of Medicine
  Minneapolis