Abstract

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.

Results

Strategy 1

The first questionnaire, done by a physician on initial 50 patient’s EMR, identified eight cases (16%) with suspected atypical diabetes mellitus. Following further manual review of the patients’ EMR, five cases were considered atypical (10%). The three excluded cases were two patients who had strong clinical characteristics of T2D and multiple family members with T2D, and one who had strong features of T2D treated with insulin. Consequently, the questionnaire was revised to avoid selecting patients as atypical in the setting of insulin treatment in patients with a phenotype of T2D because many pediatric patients with T2D are treated with insulin. The final revised questionnaire was applied to another 50 patients and identified 3 patients (6%) with possible atypical diabetes mellitus; of these, two were excluded at the stage of manual review because they lacked information regarding islet antibodies, but the clinical course suggested T1D (figure 1).

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Figure 1

Flow diagram of the process of identification of atypical diabetes mellitus cases using a questionnaire (strategy 1). EMR, electronic medical record.

Ultimately, six cases of atypical diabetes mellitus (6%) were identified out of the 100 patients screened by the questionnaire (table 1). The mean age at diagnosis was 11±2.6years, 16.6% were men, 33% non-Hispanic white (NHW) and 66.6% Hispanic (Hisp). Of the six cases, three had a clinical phenotype of T2D with onset before 10 years of age. All three had negative islet autoantibodies (including glutamic acid decarboxylase-65, insulinoma-associated antigen-2 [IA-2] and insulin autoantibodies (IAA)) and had been insulin-dependent since diagnosis. The fourth patient had a clinical diagnosis of T1D in the EMR, did not have obesity at diagnosis and had negative islet autoantibodies and a variant of unknown significance (VUS) in the PDX1 gene (heterozygous variant c.820G>T, pVal274Phe) on MODY genetic testing. The fifth patient had a clinical diagnosis of T2D in the EMR (although lacked obesity and dyslipidemia), with negative islet autoantibodies, multiple family members with ‘T2D’ and a negative MODY genetic test panel. The sixth patient had a clinical diagnosis of T1D, normal body mass index, required insulin from the time of diagnosis, had four islet autoantibodies negative (GAD65, IA-2, IAA and zinc transporter-8 (ZnT8) antibodies) and had a negative MODY genetic testing panel.

Table 1

Atypical diabetes mellitus cases identified with strategy 1 (questionnaire applied to EMR)

	Case 1	Case 2	Case 3	Case 4	Case 5	Case 6
Age (years)*	9.1	9.5	8.8	10.8	15.7	12.5
Sex	Male	Female	Female	Female	Female	Female
Race/ethnicity	Hispanic	Hispanic	NHW	Hispanic	Hispanic	NHW
BMI (%-ile)*	99.14	99.48	–	66.28	81.07	5.72
Diagnosis on EMR	T2D	T2D	T1D	T1D	T2D	T1D
Diabetes in parents	Yes	Yes	Yes	Yes	Yes	Yes
Acanthosis nigricans	Yes - minimal	Yes	No	No	No	No
C-peptide* (ng/mL)	–	3.66	–	1.44	1.04	0.46
Islet antibodies (GAD65, ICA512 and IAA)	Negative	Negative	Negative	Negative	Negative	Negative
ZnT8 antibody	Negative	–	Negative	Negative	Negative	Negative
Lipid profile*(mg/dL)	TG 114LDL 135HDL 52TChol 209	TG 277LDL 79HDL 31TChol 166Non-HDL 135	–	–	TG 150LDL 90HDL 43TChol 150Non-HDL 107	TG 102LDL 84HDL 73TChol 177Non-HDL 104
HbA1C (%)*	5.9	9.6	Not available	11.7	12.9	>14
Recent HbA1C (%)	10.8	>14	8.7	8.5	>14	8.2
Treatment*	Metformin	Insulin	Insulin	Insulin and metformin	Insulin	Insulin
MODY genetic panel	–	–	Negative	VUS on PDX1[heterozygous variant,c.820G>T (p.Val274Phe)]	Negative	Negative

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^*At diagnosis.

BMIbody mass indexEMR, electronic medical record; HDL, high-density lipoprotein; %-ile, percentile; LDL, low-density lipoprotein; MODYmaturity-onset diabetes of the young NHW, non-Hispanic white; Non-HDL, non-HDL cholesterolTChol, total cholesterol; T1D, type 1 diabetes; T2D, type 2 diabetes; TG, triglycerides

A manual review was conducted on the 89 patients’ EMR identified as typical diabetes mellitus by the questionnaire and results were similar, no further cases of atypical diabetes mellitus were identified.

The six patients with atypical diabetes mellitus identified by the questionnaire and confirmed by manual review were referred to RADIANT for further investigation. Of those patients, only four patients started enrollment in the study. Participant 1 was later found to have a pathogenic VUS for MODY and was not further enrolled. Participant 2 did not enroll. Participant 3 enrolled, on wait list for future adjudication due to mainly suspected autoantibody-negative T1D. Participant 4 enrolled and currently completing stage 2 of the study. Participant 5 enrolled but had lost contact. Participant 6 enrolled and is currently completing stage 3 of the study.

Strategy 2

We identified 68 cases of unknown diabetes mellitus type (1%, out of 6676 total patients with diabetes mellitus <21 years of age). The mean age at diagnosis was 12.6±3.3years, 32.8% were men, 23.8% NHW, 47.6% Hisp, 25.4% African American (AA) and 3.2% other. Out of 1142 children with a diagnosis of T2D in the EMR, 64 patients (6.6%) were diagnosed before age 10 years, mean age at diagnosis of 8.6±1.6years, 20.3% men, 4.7% NHW, 65.6% Hisp, 28.1% AA, 1.6% other. Out of 680 patients with new-onset T1D, 38 (5.6%) were negative for islet autoantibodies (GAD, IA-2 and IAA), mean age at diagnosis 11.3±3.8years; 57.9% men, 50% NHW, 19.4% Hisp, 22.3% AA, 8.3% other (table 2).

Table 2

Characteristics of patients identified with strategy 1 and strategy 2 (EMR generated queries to select pre-specified phenotypes of atypical pediatric diabetes)

	Strategy 1. Questionnaire	Strategy 2. EMR queries
	Atypical diabetes (n=6/100)	Unknown type (n=68/6676)	T2D<10y/o (n=64/1142)	Autoantibody negative T1D (n=38/680)
Age at diagnosis, mean±SD (y/o)	11±2.6	12.6±3.3	8.6±1.6	11.3±3.8
Sex, n (%)
Male	1 (17%)	22 (33%)	13 (20%)	22 (58%)
Female	5 (83%)	46 (67%)	51 (80%)	16 (42%)
Race/ethnicity, n (%)
Non-Hispanic white	2 (33%)	16 (24%)	3 (5%)	19 (50%)
Hispanic		33 (48%)	42 (66%)	7 (19%)
African American	4 (67%)	17 (25%)	18 (28%)	9 (22%)
Other	–	2 (3%)	1 (1%)	3 (8%)

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Unknown type: n=68/out of 6676 total of patients with diabetes under 21y/o, T2D<10y/o: n=64/out of 1142 patients with a diagnosis of T2D in the EMR, autoantibody negative T1D: n=38/out of 680 patients with new onset diagnosis of T1D.

EMR, electronic medical record; T1D, type 1 diabetes; T2D, type 2 diabetes

We conducted a manual review of the 68 cases denoted ‘unknown diabetes mellitus type’ to better delineate the forms of atypical diabetes mellitus subsumed under this category. Monogenic diabetes was suspected by the primary clinician in 41% but the majority (>80%) did not have a MODY genetic test. Of those patients who had a MODY genetic test report (n=5), four did not have any pathogenic variant in the genes included in their MODY panel and one had a variant of unknown clinical significance in one of the MODY-associated genes. 19% were classified as ‘likely T2D’ by their primary endocrinologist and 16% had a diagnosis of gestational diabetes. The remaining suspected diagnoses are summarized in table 3.

Table 3

Characteristics of patients with ‘unknown diabetes mellitus’ identified by EMR query

Cluster	N (%)
Suspected monogenic, negative MODY panel	4 (6)
Suspected monogenic, VUS	1 (1)
Suspected monogenic, MODY panel not done	23 (34)
T1D vs T2D vs monogenic, MODY panel not done	1 (1)
Syndromic	2 (3)
T1D vs T2D	3 (4)
Gestational diabetes	11 (16)
Likely T2D	13 (19)
Not determined (missing tests)	3 (4)
Known MODY diagnosis	2 (3)
Drug-induced or post-transplant vs T2D	4 (6)
Stress induced hyperglycemia	1 (1)

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EMRelectronic medical recordMODYmaturity-onset diabetes of the young T1Dtype 1 diabetesT2Dtype 2 diabetesVUSvariant of unknown significance

Conclusions

We developed two strategies to identify patients with atypical diabetes mellitus using EMR data. Using a clinical questionnaire and EMR queries we found that 1%–6.6% of pediatric patients with diabetes mellitus have atypical forms of diabetes. T1D and T2D compromise the vast majority of diabetes in the USA,¹ and the current literature suggests 1%–6.5% of children with diabetes mellitus are estimated to have atypical forms of diabetes mellitus, consistent with our observation.^{11 12}

In a prior RADIANT study, Parikh et al recently developed a data mining framework using phenotypical characteristics of two diabetes mellitus cohorts: one an adult patient cohort in a predominantly Hispanic population in South Texas, and the other a multiethnic pediatric cohort at TCH, Houston. The frequency of atypical diabetes mellitus in the adult diabetes cohort was 11.5%, whereas it was 5.3% in the pediatric diabetes mellitus cohort, very similar to the present study. In addition, the Parikh et al study demonstrated the existence of two distinct clusters of atypical diabetes mellitus phenotypes in the pediatric cohort.¹³

Of the atypical cases identified in our study, half were children with T2D diagnosed before 10 years of age. All had negative islet autoantibodies. This group exemplifies an atypical form of diabetes mellitus, since it is rare for children to be diagnosed with T2D before 10 years of age, especially if they are also pre-pubertal.^14,16 The incidence of T2D increases with age¹⁷ and several studies have shown an association between puberty timing and the development of T2D.¹⁸ Information about the stage of pubertal development was not available in all patients, therefore we cannot rule out the presence of precocious puberty that could have contributed to the earlier presentation of diabetes mellitus.

The other half of the suspected atypical cases were identified by their physicians due to a phenotype of MODY; of these, all had negative MODY gene panel testing (with one VUS). Among the atypical cases identified using strategy 2, the majority of the ‘unknown diabetes mellitus type’ group also comprised suspected MODY cases.

There are no well-defined clinical practice guidelines once a patient with atypical forms of diabetes mellitus has been identified. Most of the patients with clinically suspected MODY had received a clinical diagnosis of either T1D or T2D as documented in the EMR. Subtle clinical phenotypes such as overlapping T1D versus T2D are less likely to be studied further. Leveraging the EMR to identify patients with atypical diabetes mellitus can have direct impact both on clinical and research efforts.

From the clinical care perspective, system-wide identification and monitoring of these cases may improve clinical outcomes. From the research perspective, better identification and characterization of atypical forms of diabetes mellitus may improve enrollment in clinical trials such as RADIANT and accelerate discovery of new pathophysiologic pathways to diabetes mellitus and the possibility of targeted treatment. The questionnaire used in strategy 1 aimed to exclude the more described forms of diabetes mellitus as categorized by the American Diabetes Association: T1D, T2D, gestational diabetes mellitus and specific diabetes types due to other known causes (eg, monogenic diabetes, diseases of the exocrine pancreas and drug or chemical-induced diabetes).¹ The use of questionnaires as screening tools has proven helpful in clinical practice to identify rare forms of diabetes mellitus. For example, Shields et al developed and validated a calculator based on clinical criteria to determine an individual’s probability of having MODY as a tool for rational genetic testing with improved sensitivity and specificity for identifying MODY patients.¹⁹

In strategy 1, our questionnaire was effective in identifying atypical diabetes mellitus cases. Out of the 100 patients, only 11 required a more detailed manual review. In the clinical practice, identification of atypical diabetes mellitus may be easier and also non-biased using such a questionnaire. A questionnaire with 19 questions might seem time consuming for a busy clinical practice; however, the first 12 questions were close-ended questions with only the remaining seven questions requiring more detailed clinical information and some of those questions were not applicable to all patients. If validated, this questionnaire could potentially become a screening tool to be applied by clinicians as a guide in patients that have mixed phenotype of diabetes mellitus and may help to determine if they need further testing or referral for investigation of atypical forms of diabetes mellitus. The questionnaire featured a straightforward design primarily comprising binary questions. It could potentially serve as a self-referral tool accessible to patients or their families online. Alternatively, it could be made available to patients and families in the waiting room through an EMR-connected tablet. The latter strategy has been deemed a valuable tool in primary and specialty care clinics.^{20 21}

In strategy 2, obtaining queries of patients with diabetes mellitus categorized as ‘unknown diabetes mellitus type’ was possible mainly due to the Diabetes Flowsheet included in our EMR system that is filled out at the clinic visit only by the pediatric endocrinologist or the diabetes nurse practitioner taking care of the patient. This approach streamlined the identification of atypical forms of diabetes mellitus from a vast amount of data that would otherwise require a significant manual chart review effort to complete. Institutions that have not yet integrated diabetes mellitus flowsheets into their EMR systems may consider incorporating these tools.

Our study reported a prevalence of 5.6% of autoantibody-negative T1D cases, however the prevalence reported in children has been as high as 19%.²² The race/ethnicity proportions of patients identified by the two strategies were similar to those reported in other studies, which assessed populations composed mainly of under-represented racial and ethnic groups (primarily Hisp and AA).^{23 24} However, in the subset of autoantibody-negative T1D cases identified using strategy 2, NHW (50%) and AA (22%) children comprised the majority of cases. Wang et al reported no significant racial/ethnic difference in prevalence of autoantibody-negative diabetes in younger children with newly diagnosed diabetes mellitus. However, in children older than 14 years, autoantibody-negative diabetes was much more prevalent in under-represented racial/ethnic groups compared with NHW (57.1% in Hisp, 70% in AA and 25.9% in NHW), due in part to a higher rate of T2D in Hisp and AA.²² Individuals from under-represented racial/ethnic groups with T1D and T2D have increased morbidity and poor long-term control of diabetes mellitus overall,^25,27 yet very little is known on the prognosis of the atypical forms of diabetes mellitus that appear to be highly prevalent in these groups. Our approach allowed us to identify a significant number of children from under-represented racial/ethnic groups who are less likely to be referred for further evaluation due to multiple barriers to participation in biomedical research.¹⁰ Hence, it is important for physicians to be familiar with the concept and forms of atypical diabetes mellitus in persons belonging to underrepresented racial/ethnic groups.

The strength of our study is the use of an unbiased approach by leveraging EMR to identify pediatric patients with atypical diabetes mellitus. The limitations include that determination of atypical nature of a particular case was entirely limited to medical documentation in EMR. Also, EMR systems are designed differently, and the diabetes flowsheet used in this study might not be adaptable across organizations, limiting the use of our current approach. However, EMR usually has a significant amount of data for each patient enabling it as a valuable tool for screening purposes.

In conclusion, EMR-based approach revealed that approximately 1%–6.6% of pediatric diabetes mellitus cases are atypical. More studies are required to validate our clinical questionnaire and to streamline the process of EMR-based identification of atypical cases.

supplementary material

Footnotes

Contributor Information

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References