Exploring the diagnostic yield of family screening and genetic testing in adolescent individuals with pre-clinical phenotypes

Abstract Introduction Family screening and genetic testing are key components in the management strategy of individuals diagnosed with an inherited cardiac condition (ICC). Disease penetrance for most ICCs, notably cardiomyopathies is age dependent, which is why a more permissive approach towards family screening is adopted in young individuals with a pre-clinical phenotype. Study Objectives The main objective of this study was to explore the role of family screening and genetic testing in adolescent subjects with a pre-clinical phenotype has not been formally explored. Methodology Adolescent probands with a pre-clinical phenotype following a national cardiac screening program (BEAT-IT) were offered genetic testing and family screening. Probands with anterior TWI were rescreened at 16 years. Only those with persistent changes were enrolled in the study. Genetic counselling was also offered to probands and relatives. Testing was initially offered to first degree relatives. Cascade testing (clinical and genetic) was also offered to other generations if a screened relative satisfied one or more of these conditions i) phenotype positive, ii) pre-clinical phenotype, iii) clinically relevant genotype. Results 16 probands (mean age 15 years) were identified with a pre-clinical phenotype. All had an abnormal ECG (9=inferior/lateral TWI, 6=anterior TWI, 1=ST depression). A comprehensive evaluation was otherwise normal. Half were gene positive (G+), 4 had clinically relevant genotypes (n=4 inferior/lateral TWI). These were classified as likely pathogenic according to ACMG criteria (n=2 MYH7, n=1 ACTC1, n=1 MYBPC3). 71 family members were subsequently screened (59.2% female, median 43Y [IQR 27] at evaluation, 11.3% <18Y at evaluation, 67.6% first degree relatives). A substantial proportion (n=13, 18.3%) were referred for further evaluation. Two (2/8, 25.0%) were <18Y. An abnormal ECG was the commonest reason for referral (n=9, 12.7%). Three (4.2%) were given a diagnosis (n=2 HCM [both MYH7}, n=1 DCM [ACTC1]). Seven (9.9%) were referred because of an abnormal ECG (n=3 inferolateral TWI, n=2 ventricular ectopics, n=1 anterolateral TWI, n=1 ST depression). Four were G+ and were offered surveillance. Fourteen (19.7%) were offered family screening because of incorporating genetic testing into the study protocol. Genetics altered the evaluation strategy in 16.9% of screened relatives. More in-depth cascade testing identified 6 (8.5%) individuals who needed follow-up (n=1 diagnosis [DCM], n=1 abnormal ECG, n=4 G+). Gene negative individuals (6, 8.5%) were safely reassured and discharged. Conclusion Family screening in adolescent probands with pre-clinical phenotypes offers a reasonable diagnostic yield (4.2% diagnosis, 14.1% surveillance). Incorporating genetic testing into the evaluation protocol offers a more personalized strategy, altering management in a significant proportion of screened relatives (16.9%).