Practice-Based Insights into Adult Genetics: High Diagnostic Yield, Demographic Determinants, and Patterns of Test Utilization in Over 7,000 Patients

Precision medicine increasingly relies on genetic testing for individualized care, yet the practice patterns of genetic evaluation in adults remain under-characterized and few guidelines exist to inform appropriate testing. We analyzed eight years of electronic health record (EHR)-linked data from a high-volume adult genetics clinic (9,867 visits) within a major academic health system to define referral patterns, test utilization, and genetic testing outcomes across indications and demographic groups. Genetic testing was ordered for 52% of all new patients, with significant indication-specific variation in ordering propensity. Overall, 24% of all tests returned a diagnostic result. Diagnostic yield differed markedly by testing modality: whole-exome sequencing yielded diagnoses in 40% of patients, whereas next-generation sequencing panels, the most frequently ordered testing type, yielded diagnoses in only 16%. Although diagnostic yield declined with increasing patient age it remained above 17% in every age stratum, with the yield of exome/genome sequencing remaining above 30% across all age groups. Outcomes varied significantly by referral indication, with some yielding high rates of pathogenic findings, and others more often yielding negative or uncertain results. Operational factors materially shaped practice: test type and laboratory utilization shifted significantly over time in step with payer and testing lab policy changes. Together, these practice-based data establish adult genetics as a high-yield and important clinical domain. Our findings provide actionable evidence to inform age- and indication-aware triage, guide workforce planning, promote adult-focused practice guidelines, and advance the integration of genomic medicine into routine adult patient care.