Introduction
Type 1 diabetes (T1D) and type 2 diabetes (T2D) mellitus are heterogeneous diseases in which clinical presentation and disease progression may vary significantly within and between diabetes types.1 Furthermore, data obtained using molecular diagnostic methods and deep phenotyping techniques indicate the presence of atypical forms of diabetes mellitus with varied pathophysiology.2 Atypical diabetes mellitus comprises both rare genetic syndromes and clusters of phenotypically distinct forms of diabetes mellitus within a spectrum between classically presenting T1D and T2D.3 4
Atypical forms of diabetes mellitus are suspected clinically when diagnostic criteria and clinical phenotype do not meet usually accepted definitions of ‘classic’ T1D or T2D. T1D is characterized by evidence of islet autoimmunity (positivity for islet autoantibodies), rapid progression to near-complete insulin deficiency, insulin dependence, development of diabetic ketoacidosis if insulin therapy is interrupted, younger age of presentation and usually lack of obesity or evidence of insulin resistance. T2D is characterized by overweight/obesity and insulin resistance, older age at diagnosis, family history of diabetes mellitus, lack of insulin dependence (at least initially) and slowly progressing beta cell dysfunction. However, there is clearly heterogeneity within each of these types of diabetes mellitus, and investigations of these heterogenous forms have led to the identification of some well-characterized atypical diabetes syndromes such as latent autoimmune diabetes of adults and subtypes of ketosis-prone diabetes (KPD).5–7
Identification and characterization of atypical forms of diabetes mellitus that do not fit the classic definitions of T1D and T2D could improve the clinical classification of the condition and provide a foundation for ‘precision diabetes’ and targeted treatment. The value of this approach is evident from the considerable impact of identifying and characterizing monogenic forms of diabetes (maturity-onset diabetes of the young (MODY) and neonatal diabetes), which has dramatically improved the management of these patients with targeted therapies and family screening.7 8
Careful study of atypical forms of diabetes mellitus could also elucidate the complex pathophysiology underlying the common types of diabetes mellitus, by providing insight into new mechanisms that explain the heterogeneity of phenotypes in both ‘T1D’ and ‘T2D’.9 The Rare and Atypical Diabetes Network (RADIANT) is a group of universities, hospitals and clinics across the USA that aims to discover and define rare and atypical forms of diabetes mellitus through detailed phenotyping and genotyping of the participants and families referred for study.4
Because of a lack of established criteria to define ‘atypical diabetes’, assembling a cohort of pediatric patients with atypical diabetes mellitus to allow meaningful studies remains challenging. In addition, participants ascertained by self-referral or referral by healthcare providers have been shown to lack racial and ethnic diversity.10 On the other hand, the electronic medical records (EMR) provides a unique opportunity to identify individuals with atypical forms of diabetes mellitus in a more inclusive manner, utilizing data collected as part of routine clinical care. However, strategies to ‘query’ EMR databases need to be developed, as most such databases lack specific codes for atypical forms of diabetes mellitus. In this study, we aimed to identify diverse cases of rare or atypical pediatric diabetes mellitus in an extensive EMR database, as a foundation for future recruitment of participants in research studies such as RADIANT to understand their etiologies and pathogenesis. We hypothesized that systematic review of large EMR systems with prespecified criteria may facilitate the identification of diverse children with atypical forms of diabetes mellitus.
Research design and methods
We tested two strategies to query an EMR database (ie, Epic) for atypical diabetes mellitus cases at Texas Children’s Hospital (TCH), Houston, Texas. In strategy 1, we designed a questionnaire to rule out patients with typical diabetes mellitus, and this questionnaire was applied by a manual review of EMR. The questionnaire was designed to be used either by the patient (as self-referred) or by a physician. For this study, a physician (MFA) reviewed the EMR of 50 youth (0–21 years) with diabetes mellitus seen consecutively in the TCH Diabetes Outpatient Clinic in April 2019 and responded the questionnaire with the information available from the EMR of each patient. After revisions for clarity, a second version of the questionnaire was applied by the same physician (MFA) on 50 additional patients seen during the same month. Sex, race and ethnicity data were self-reported by parents and/or patients and available as documentation on the EMR.
The revised questionnaire included 19 questions (online supplemental material S1), many focused on excluding patients with gestational diabetes and diabetes associated with chronic corticosteroid use, cystic fibrosis, pancreatectomy, chronic pancreatitis, HIV infection or HIV medications, hemochromatosis, Cushing syndrome, acromegaly and lipodystrophy (questions 1–11). Other questions aimed to rule out classic T1D based on clinical presentation and presence of islet autoantibodies (questions 12–13) and to rule out T2D based on the clinical diagnosis documented in the EMR, presence of obesity or hypercholesterolemia at time of diagnosis (question 14). Subsections of question 14 aimed to identify patients with KPD and children diagnosed with T2D under the age of 10 years old for inclusion. Since the goal was to identify previously unknown forms of rare and atypical diabetes mellitus, subsequent questions aimed to exclude known forms of atypical diabetes mellitus including monogenic diabetes (question 15–16) and Wolfram syndrome, Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes and Maternally Inherited Diabetes and Deafness syndromes (question 17). At the end of the questionnaire, two free-text questions (questions 18 and 19) were included that could potentially be used for descriptions of suspected atypical features noted by individuals or their physicians.
The application of this questionnaire to the EMR of each patient took approximately 5–10 min, depending on how readily available the information was in their medical record.
In strategy 2, we aimed to identify three categories of atypical forms of diabetes mellitus using data from an available Diabetes Flowsheet embedded in the clinical encounter that must be completed by the treating pediatric endocrinologist or nurse practitioner as a mandatory part of the medical documentation for each outpatient visit. The Diabetes Flowsheet includes a question on diabetes type with a set of options including T1D, T2D, monogenic diabetes, steroid-induced diabetes, drug-induced diabetes, cystic fibrosis-related diabetes and ‘unknown’ diabetes type. In collaboration with EMR analysts, we built three electronic queries to generate reports of patients up to 21 years of age who attended the TCH Diabetes Outpatient Clinic from April 2019 to March 2020 and had diabetes mellitus of unknown type, T2D diagnosed before 10 years of age or autoantibody-negative T1D. The queries used data from Diabetes Flowsheet and demographic information including age, sex, race and ethnicity. We performed manual review of the participants under the category of unknown diabetes mellitus to better determine their characteristics.
Characteristics of both strategies were summarized using descriptive statistics.