Ask a Specialist: Glucose Testing Follow-Up

Ask a Specialist: Glucose Testing Follow-Up 150 150 Rohan Henry, MD, MS

For a patient with obesity and polycystic ovarian syndrome (PCOS) with impaired glucose tolerance on an oral glucose tolerance test, how often should her glycemia be tested? And with which test?


Pediatric research studies addressing this specific question are lacking. A gap in the literature involving natural history studies makes it difficult to predict the progression of impaired glucose tolerance to overt type 2 diabetes.

The oral glucose tolerance test (OGTT) is viewed as superior to the fasting blood glucose test in determining if a patient has early diabetes. This is based on the fact that the 2-hour post-prandial glucose level becomes abnormal, even before the fasting blood glucose level is affected, during the development of diabetes. The OGTT is a laborious test, however. This, combined with a lack of useful research studies, has resulted in no current formal guidelines or recommendations for testing.

Given the concern about someone who may be on a path of progression to type 2 diabetes and who has chosen lifestyle changes over medication as an initial response, it may be wise to pair an initial OGTT with an HbA1c. With this in mind, a period of at least 3-6 months between testing is a reasonable recommendation, given that the HbA1c represents a 3-month snapshot of glycemic control.

Another reason for pairing the HbA1c with the OGTT initially is that the former is a poor diagnostic tool when used in isolation for assessing prediabetes and type 2 diabetes in obese children.(1)  By pairing these two tests, you will have a reference point that serves as a guide as to how to interpret the HbA1c result. Thus, you can decide how to proceed in the future. With HbA1c results above 6% there may be a higher risk of actual progression of dysglycemia (IGT progressing to frank diabetes). It should be noted that the HbA1c may not be useful in the presence of hemoglobinopathies and states such as iron deficiency anemia.

Because the HbA1c is a 3-month snapshot of glucose control, inevitably some patients progress from a status of having IGT to type 2 diabetes in the interim before the HbA1c becomes abnormal. In such cases, patient education is key! Patients and families should be advised of the symptoms of diabetes and that when such symptoms are present, they should be reported to their health care provider.

A recently published study examined the perceptions of physicians, patients and parents surrounding the pediatric type 2 diabetes diagnosis. Based on the responses, the authors theorized that if the symptoms of diabetes had been better comprehended by patients, an earlier type 2 diabetes diagnosis could have been made.(2) Patient understanding, recognition and communication of symptoms to their health care provider is really important.

Relevant Resources:

  1. Nowicka P, Santoro N, Liu H, Lartaud D, Shaw MM, Goldberg R, et al. Utility of hemoglobin A(1c) for diagnosing prediabetes and diabetes in obese children and adolescents. Diabetes Care. 2011;34(6):1306-11.
  2. Xu J, Pratt K, Chaudhari M, Henry R, Hubbard RA, Siegel R, et al. On a Different Page! Perceptions on the Onset, Diagnosis, and Management of Type 2 Diabetes Among Adolescent Patients, Parents, and Physicians. Glob Pediatr Health. 2021;8:2333794X211046430.

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