Type 2 Diabetes

Letter to the Editor Re: Vijan S. Type 2 Diabetes. Ann Intern Med. 2019; 171(9):ITC65-ITC80.

Shen Tian*, Juan Wu*, Jia-shuo Liu, Bao-shan Zou, Ling-quan Kong#
* These authors have contributed equally to this work.
Department of Endocrine and Breast Surgery, the First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China
Correspondence to:
#Dr. Ling-quan Kong, Department of Endocrine and Breast Surgery, the First Affiliated Hospital of Chongqing Medical University

To the editors: A recent review by Vijan (1) summarized the evidence supporting diabetes prevention and treatment. But some misleading information exists in the review concerning the diagnosis and prevention of type 2 diabetes.
First, the criteria for diagnosis of diabetes in the review are not consistent with the current 2019 American Diabetes Association (ADA) recommendations. In the “Diagnosis and Evaluation” part, the author stated “diabetes can be diagnosed in persons with classic symptoms and a nonfasting glucose level of 11.1 mmol/L (200mg/dL) or higher ……” But “nonfasting glucose” is unequivalent to “random glucose”. Virtually the 2019 ADA guideline (2) pointed out the person with classic symptoms and random plasma glucose level (instead of nonfasting glucose level) ≥ 11.1 mmol/L (200 mg/dL) will be diagnosed with diabetes. Additionally, in the “CLINICAL BOTTOM LINE” of this part, the diagnosis of type 2 diabetes can be confirmed by “fasting plasma glucose (FPG) levels above 7.0 mmol/L (>126 mg/dL) on 2 occasions at least 1 day apart”. However, according to ADA recommendations (2), a person with FPG level of exactly 7.0 mmol/L (126 mg/dL) should also be diagnosed with diabetes.
Second, in the review, the author developed a table (Table 1) to summarize the diagnostic criteria for diabetes or prediabetes, but it was not complete. According to current ADA and WHO guidelines for diabetes or prediabetes (2,3), the diagnostic criteria for diabetes include FPG value, HbA1c criteria, 2-h plasma glucose (2-h PG) value during a 75-g oral glucose tolerance test (OGTT) or classic symptoms plus random glucose level; the diagnostic criteria for prediabetes include FPG value, HbA1c criteria or OGTT with 2-h PG value. But the standards of OGTT and random glucose for diabetes diagnosis and the standard of OGTT for prediabetes diagnosis are not included in the Table 1 of this review. In fact, the title of the Table 1 should be “Diagnostic Criteria for Type 2 Diabetes or prediabetes” instead of “Diagnostic Criteria for Type 2 Diabetes”. Table makes article more concise and should be accurate and comprehensive to guide doctors’ clinical practice.
Third, the author listed Finnish Diabetes Prevention Study (FDPS), Da Qing Diabetes Prevention Study (DQDPS) and Study to Prevent Non-Insulin-Dependent Diabetes Mellitus (STOP-NIDDM) to indicate the progression from impaired glucose tolerance (IGT) to diabetes can be prevented. But the evidences are not well established. All the IGT population enrolled in these above-mentioned studies were diagnosed according to the outdated 1985 WHO diagnostic criteria (4). Actually according to the current WHO or ADA criteria, those participants with an initial FPG of 7.0-7.7 mmol/L should have been diagnosed with diabetes, instead of IGT. The update of diagnostic and inclusion criteria in clinical trials should not be ignored (4). Thus, the original results of these studies cannot be directly applied to the current IGT population diagnosed by the current WHO or ADA criteria. The supporting evidence of diabetes prevention should be quoted in a more statistically accurate and scientifically serious way.

Potential Financial Conflicts of Interest: None disclosed

References:
1. Vijan S. Type 2 Diabetes. Ann Intern Med. 2019;171(9):Itc65-itc80.
2. American Diabetes Association, 2. Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes-2019. Diabetes care 2019; 42(Suppl 1): S13-s28.
3. World Health Organization. Definition and diagnosis of diabetes mellitus and intermediate and hyperglycaemia. Report of a WHO/IDF consultation.
http:// www.who.int/diabetes/publications/diagnosis_diabetes2006/en/ (November 24 2019)
4. Li H, Tian S, Wu J, Xu Z, Kong LQ. Diagnostic criteria should be considered when reviewing the effect of diabetes prevention studies. Diabetologia 2019; 62(11): 2163-5.

Disclosures: None disclosed

The comments are correct that the following corrections need to be made to the “Clinical Bottom Line” section under “Diagnosis and Evaluation”: the diagnostic criteria for diabetes should be greater than or equal to 126, rather than greater than 126. The values in the Table are accurate but the table should also be more accurately titled “Diagnostic criteria for diabetes and prediabetes”.
The commenters note that non-fasting glucose is not entirely equivalent to random glucose. I agree that the terminology should be better aligned with the ADA for consistency. However, in practice this is of minimal consequence as patients are either fasting, and the diagnosis can be made with a fasting plasma glucose of greater than or equal to 126; or patients are not fasting, and can be diagnosed with symptoms and a glucose >=200. These criteria for diagnosis with random glucose and OGTT were not included in the table to keep the table concisely focused on the primary methods of diagnosis, but the values are in fact cited in the text.
The commenters also are correct that the diagnostic criteria in the older diabetes prevention studies are different than current definitions. An in-depth discussion of those points is beyond the scope of this article, which is a broad clinical summary rather than a focused review of diabetes prevention. However, it is important to recall that glucose is a continuous risk factor for vascular complications, and decisions about diagnostic thresholds depend on one’s preferences for sensitivity vs. specificity of the cutoffs. The important point is that, regardless of thresholds for diagnosis, there is clear evidence that that there are strategies that can reduce blood glucose and therefore lower the risk of diabetes.