I would like to draw the attention to Dr. Winter's statement in response, "there is no additional diagnostic information that is derived from more time points between fasting and 2 hours, nor is more diagnostic information provided by time points beyond 2 hours".
In practice, we come across OGTT results where both fasting as well as 2 hr post glucose glucose are well within the limits but only one are two results between zero and 2 hrs going above 140 mg/dL. In the classification well known before, it was termed impaired glucose tolerance which is a pre-diabetic state. Hence the points between zero and two hrs certainly are of value especially in patients who are having family history of diabetes or diabetic risk factors eg., central obesity but who are asymptomatic and normoglycemic during presentation to the clinic. It may be argued that HbA1c can be used to unmask such cases. Unless the role of HbA1c in detecting pre-diabetic state is well established, in my opinion it cannot be used for the said purpose.
Dr. Venkatesh Dambala
Consultant - Clinical Biochemistry
Apollo Bramwell Hospital, Mauritius