Rethink Monogenic Diabetes Screening: Use Body Mass Index Plus Targeted Testing
In an ancestrally diverse pediatric cohort with clinician-diagnosed type 2 diabetes (ProDiGY; 82% non-White; autoantibody-negative), investigators evaluated whether the adult-derived maturity-onset diabetes of the young (MODY) probability calculator could distinguish monogenic diabetes (MODY) from youth-onset type 2 diabetes. Exome sequencing across 10 ClinGen-endorsed MODY genes identified 100 MODY cases (3%) among 3,379 participants, most commonly in HNF1A (41%), GCK (27%), HNF4A (26%), with smaller contributions from PDX1 (4%) and INS (2%). Performance was assessed at the earliest post-diagnosis time point per calculator specifications, using participants from SEARCH, TODAY, and TODAY Genetics.
Among those with complete data (44 MODY; 694 type 2 diabetes), the MODY calculator failed to add clinical utility over simple anthropometrics: its variables achieved an area under the curve (AUC) of 0.82—no better than body mass index (BMI) alone (AUC 0.82). The adult trigger threshold (>25% probability) captured 98% of MODY but also 92% of type 2 cases, yielding only a 6.3% positive rate; even >75% probability had a 7% yield. BMI was the strongest single predictor, while age at diagnosis had modest discrimination (AUC 0.63) and HbA1c or “on any medication” had none (AUC ~0.51). Parental diabetes did not differentiate groups (≈74% in both), though having two affected parents was more common in type 2 diabetes. Lower BMI enriched for MODY (eg, ≤25 kg/m²), but this strategy would miss approximately 45% of cases, and most youth with MODY were still overweight/obese by pediatric percentiles. Other helpful markers included fasting insulin and waist circumference (both AUC 0.81), C-peptide (0.80), and fibrinogen (0.77). Overall, the adult-validated calculator underperforms in youth; BMI-based screening thresholds may be a pragmatic stopgap that should vary by ancestry, but new (ideally gene-specific) biomarkers are needed to reliably distinguish MODY from youth-onset type 2 diabetes.
Reference: Kreienkamp RJ, Shields BM, Pollin TI, et al. MODY Calculator and Clinical Features Routinely Used to Distinguish MODY From Type 2 Diabetes in Adults Perform Poorly for Youth Clinically Diagnosed With Type 2 Diabetes. Diabetes Care. 2025 Jan 1;48(1):e3-e5. doi: 10.2337/dc24-1565.
Mayra Cantazaro
DNP, FNP-BC, BC-ADM, CDCES