ADA Acknowledges “Misdiagnosis is Common,” CDC Indirectly Acknowledges Undercounting of Cases of Type 1 Diabetes

Twenty-five years ago, I began my advocacy on behalf of people with adult-onset Type 1 diabetes, shortly after I was misdiagnosed at age 35.  At that time, it was the position of the American Diabetes Association (ADA) and Centers for Disease Control and Prevention (CDC) that Type 1 diabetes was a childhood disease, and the organizations did not acknowledge misdiagnosis as a problem.  Back then, doctors would become enraged when I used the term “misdiagnosis.”  Finally, more than a quarter century later, the ADA has stated that misdiagnosis is common (since Type 1 and Type 2 are altogether different diseases, yes, it is misdiagnosis).  Additionally, CDC’s National Diabetes Statistics Report 2020 indirectly references the problem of undercounting of Type 1’s and misdiagnosis, by categorizing people who self-report in surveys that they went on insulin within one year of diagnosis as having Type 1 diabetes.

These changes from leading organizations are very positive—we have come a long way, but we are not there yet.  Misdiagnosis and undercounting continue to hamper people’s access to the appropriate care and treatment of Type 1 diabetes.  But this change of position by the ADA and CDC is a fantastic step which will hopefully pave the way for people with adult-onset Type 1 diabetes to receive a correct diagnosis, appropriate care, and overall better outcomes.

In this blog I provide excerpts from ADA’s Standards of Medical Care in Diabetes 2020 and CDC’s National Diabetes Statistics Report 2020.

Here are some pearls from ADA Standards of Medical Care in Diabetes 2020 [all emphasis is mine]:

“Type 1 diabetes and type 2 diabetes are heterogeneous diseases in which clinical presentation and disease progression may vary considerably. Classification is important for determining therapy, but some individuals cannot be clearly classified as having type 1 or type 2 diabetes at the time of diagnosis. The traditional paradigms of type 2 diabetes occurring only in adults and type 1 diabetes only in children are no longer accurate, as both diseases occur in both age-groups. Children with type 1 diabetes typically present with the hallmark symptoms of polyuria/polydipsia, and approximately one-third present with diabetic ketoacidosis (DKA). The onset of type 1 diabetes may be more variable in adults; they may not present with the classic symptoms seen in children and may experience temporary remission from the need for insulin.

It is important for the provider to realize that classification of diabetes type is not always straightforward at presentation and that misdiagnosis is common (e.g., adults with type 1 diabetes misdiagnosed as having type 2 diabetes; individuals with maturity-onset diabetes of the young [MODY] misdiagnosed as having type 1 diabetes, etc.). Although difficulties in distinguishing diabetes type may occur in all age-groups at onset, the diagnosis becomes more obvious over time.

Characterization of the underlying pathophysiology is more developed in type 1 diabetes than in type 2 diabetes. It is now clear from studies of first-degree relatives of patients with type 1 diabetes that the persistent presence of two or more islet autoantibodies is an almost certain predictor of clinical hyperglycemia and diabetes. The rate of progression is dependent on the age at first detection of autoantibody, number of autoantibodies, autoantibody specificity, and autoantibody titer.

There is debate as to whether slowly progressive autoimmune diabetes with an adult onset should be termed latent autoimmune diabetes in adults (LADA) or whether the clinical priority is awareness that slow autoimmune β-cell destruction means there may be long duration of marginal insulin secretory capacity. For the purpose of this classification, all forms of diabetes mediated by autoimmune β-cell destruction are included under the rubric of type 1 diabetes.

Immune-mediated diabetes, previously called “insulin-dependent diabetes” or “juvenile-onset diabetes,” accounts for 5–10% [Note 1] of diabetes and is due to cellular-mediated autoimmune destruction of the pancreatic β-cells. Autoimmune markers include islet cell autoantibodies and autoantibodies to GAD (GAD65), insulin, the tyrosine phosphatases IA-2 and IA-2β, and zinc transporter 8 (ZnT8). The disease has strong HLA associations, with linkage to the DQA and DQB genes. These HLA-DR/DQ alleles can be either predisposing or protective.

The rate of β-cell destruction [in Type 1 diabetes] is quite variable, being rapid in some individuals (mainly infants and children) and slow in others (mainly adults). Children and adolescents may present with DKA as the first manifestation of the disease. Others have modest fasting hyperglycemia that can rapidly change to severe hyperglycemia and/or DKA with infection or other stress. Adults may retain sufficient β-cell function to prevent DKA for many years; such individuals may have remission or decreased insulin needs for months or years and eventually become dependent on insulin for survival and are at risk for DKA

Although patients are not typically obese when they present with type 1 diabetes, obesity is increasingly common in the general population and there is evidence that it may also be a risk factor for type 1 diabetes. As such, obesity should not preclude the diagnosis.”

Melitta’s Note 1:  Type 1 diabetes that is correctly diagnosed accounts for 5-10% of all cases of diabetes.  However, as the Standards of Care point out, misdiagnosis is common, and in fact ~10% of people diagnosed with “Type 2” diabetes are autoantibody positive, have been misdiagnosed, and in fact have Type 1 diabetes.  Therefore, Type 1 diabetes represents more than 5-10% of all cases of diabetes.  See the CDC National Diabetes Statistics Report for additional information.

CDC National Diabetes Statistics Report 2020

“Most estimates of diabetes in this report do not differentiate between type 1 and type 2 diabetes. However, as type 2 diabetes accounts for 90% to 95% of all diabetes cases, the data presented here are more likely to be characteristic of type 2 diabetes, except as noted.

Prevalence of diagnosed diabetes:

• 210,000 children and adolescents younger than age 20 years—or 25 per 10,000 US youths— had diagnosed diabetes. This includes 187,000 with type 1 diabetes.
• 1.4 million adults aged 20 years or older—or 5.2% of all US adults with diagnosed diabetes—reported both having type 1 diabetes and using insulin.
• 2.9 million adults aged 20 years or older—or 10.9% of all US adults with diagnosed diabetes—started using insulin within a year of their diagnosis

APPENDIX B of the National Diabetes Statistics Report: Detailed Methods and Data Sources: Validated methods to distinguish between types of diabetes in surveys are not available. The percentage of adults aged 20 years or older with diagnosed diabetes who self-reported type 1 diabetes plus current insulin use and the percentage of adults aged 20 years or older with diagnosed diabetes who started using insulin within a year of their diagnosis were estimated from 2017 NHIS data. To estimate the number of adults aged 20 years or older with type 1 diabetes, these percentages were then applied to the derived number of adults aged 20 years or older with diagnosed diabetes.”