MON-563 A Single Center, Cross Sectional Prevalence Study of Maturity-Onset Diabetes of the Young (MODY) in Patients Diagnosed with Type 2 Diabetes Mellitus (DM)

Abstract Disclosure: G. Arora: None. P. Drazkowski: None. S. Azad: None. V. Perugu: None. J. Batra: None. A. VanStory: None. I. Johnson: None. K. Samson: None. C.V. Desouza: None. Introduction: MODY is often misdiagnosed as type 1 or type 2 DM . Its prevalence is estimated to be 1-3% of all cases of DM. To date, mutations in at least 14 different genes have been associated with a MODY phenotype. Distinguishing patients who have rare forms of diabetes such as MODY from those with type 1 or type 2 DM is a diagnostic challenge due to similar clinical features. Purpose: To determine the prevalence of MODY among patients diagnosed with type 2 DM using the Exeter Diabetes MODY Calculator. Methodology: First Phase - Retrospective Review: Inclusion criteria: Age 19 - 50 years, diagnosis of type 2 DM or “other specified diabetes or MODY”, age <35 years at diagnosis of type 2 DM, HbA1c <7.6%, BMI <30. Exclusion criteria: type 1 DM, current pregnancy. After IRB approval, Electronic Medical Records (EMR) were reviewed and MODY probability calculated using the Exeter Diabetes MODY Calculator (EDMC). Those with probability >20% were contacted to participate in phase 2 of the study. For patients with diagnosis "other specified diabetes or MODY", records were reviewed to confirm that genetic testing was performed; if not, they were invited to participate in phase 2 of the study. Second Phase - Prospective Follow-up: Eligible participants were directed to lab and then genetic testing using Invitae Monogenic Diabetes Panel kit. Participants who tested positive for MODY via genetic testing met with the genetic counselor to review results, discuss diagnostic implications, review inheritance patters and options for genetic testing in family members. Different cut-offs for EDMC scores were used to calculate sensitivity and specificity for detecting MODY-specific genes (pathogenic variants - PV and undetermined significance variants - USV). Results: EMRs of 879 patients were reviewed - 38 were eligible for phase 1, 21 enrolled for phase 2, and 12 completed phase 2, as of now. Of note, 2/12 patients were found to have PV and 3/12 were found to have USV.Using a >35% cut off for EDMC score yielded 100% sensitivity and 57% specificity. Using a >75% cutoff for EDMC score yielded 60% sensitivity and 100% specificity. Conclusion: The prevalence of MODY among patients diagnosed with type 2 DM and >20% probability calculated from MODY calculator in our high-risk population was 17%, which is significantly higher than the prevalence of MODY in type 2 DM. However, 25% (3/12) participants who completed phase 2 were found to have USV, which may or may not have implications. The sensitivity and specificity of the EDMC depends on the probability percentage cut off used, and the choice of optimal cutoff depends on the desired balance of sensitivity and specificity in a specific population. Presentation: Monday, July 14, 2025