The value of age of onset and family history as predictors of molecular diagnosis in a Swedish cohort of inherited retinal disease.

PURPOSE: This study aimed to characterize clinical and genetic findings in a Swedish cohort with inherited retinal disease (IRD), identify predictors for achieving a molecular diagnosis and evaluate the effects of increased genetic testing over time. METHODS: Clinical and genetic data from 324 nonrelated IRD index individuals referred for genetic testing in the Stockholm region between 2016 and 2023 were collected retrospectively and analysed by clinical subtype, age of onset and testing period (2016-2020 vs. 2021-2023). Logistic regression was used to calculate odds ratios for age of onset and family history on the likelihood of achieving a molecular diagnosis. RESULTS: The diagnostic yield was 55% and involved 56 genes. In 10% of solved individuals, the molecular diagnosis refined the clinical diagnosis. For each 1-year increase in age of onset, the odds of achieving a molecular diagnosis decreased by 3% (odds ratio 0.97, 95% confidence interval 0.96-0.98). A positive family history doubled the odds (odds ratio 2.1, 95% confidence interval 1.3-3.4). The use of genetic testing increased 2.1-fold and the number of molecular diagnoses increased 1.6-fold relative to the population of the Stockholm region between the two testing periods. CONCLUSION: This study adds to the knowledge of the clinical and genetic landscape of IRDs in Sweden and establishes age of onset and family history as significant predictors for achieving a molecular diagnosis. Increased genetic testing on a population level substantially increased the number of individuals receiving a molecular diagnosis with a high diagnostic yield compared to other rare diseases.