Parents' interest in genetic testing of their offspring in multiplex epilepsy families.

Objective: To evaluate parents' interest in genetic testing of their offspring in families containing multiple individuals with epilepsy.

Methods: Seventy-seven parents with affected offspring and 173 parents without affected offspring from families containing multiple individuals with epilepsy completed a questionnaire asking about their interest in genetic testing of their offspring. Interest in testing was ascertained in four scenarios defined by clinical utility and penetrance of the gene in the test (100% vs. 50%). Pairwise agreement in interest was assessed between parents for testing themselves versus their offspring, and between mothers and fathers for their offspring.

Results: Among parents with affected offspring, the proportion interested in genetic testing of offspring ("diagnostic testing") was 86% in the 100% penetrance, clinical utility scenario, and 71% in the 100% penetrance, no clinical utility scenario (p = 0.007). Among parents without affected offspring, comparable proportions interested in genetic testing of offspring ("predictive testing") were 74% and 53% (p < 0.001), and were significantly lower than in parents with affected offspring (clinical utility, p = 0.02; no clinical utility, p = 0.01). Interest in testing did not differ by gene penetrance. Parents' agreement in testing interest for themselves versus their offspring was "substantial" (90% agreement, κ = 0.72) for a test with clinical utility, and "almost perfect" for a test without clinical utility (94% agreement, κ = 0.88). Agreement in testing interest between mothers and fathers was "moderate" for a test with clinical utility (85% agreement, κ = 0.48,), and "fair" for a test without clinical utility (67% agreement, κ = 0.30).

Significance: Interest in diagnostic genetic testing is strong among parents with offspring with epilepsy, particularly when the test offers clinical utility. Testing interest is lower for a diagnostic test without clinical utility, or for a predictive test in offspring at risk of developing epilepsy in the future.