# Contribution of genetic test results to patient management in ophthalmology: results from a Turkish Stargardt disease cohort

## TL;DR

This study shows how genetic testing and collaboration between ophthalmologists and geneticists improves the diagnosis and management of Stargardt disease in Turkish patients.

## Contribution

The study reports three novel ABCA4 gene variants and highlights genotype-phenotype correlations in Turkish Stargardt disease patients.

## Key findings

- Genetic testing confirmed Stargardt disease in 54% of patients and revised diagnoses in 10%.
- Three novel ABCA4 variants were identified in Turkish patients.
- Biallelic severe ABCA4 variants correlated with earlier disease detection.

## Abstract

The aim of the study was to analyze the genotype and phenotype characteristics of Turkish patients with a clinical diagnosis of Stargardt disease and to evaluate how collaboration between the departments of medical genetics and ophthalmology contributes to patient management.

The clinical findings, genetic testing workflow in the medical genetics department, and the genetic testing results of patients clinically diagnosed with Stargardt disease in the ophthalmology department were retrospectively analyzed.

The study included 50 patients from 46 families. The genetic test reports confirmed the clinical diagnosis of Stargardt disease type 1 (STGD1) in 27 patients (54%), led to revision of the clinical diagnosis in five patients (10%), and were inconclusive in 18 patients (36%). A total of 26 pathogenic ABCA4 variants were reported in 39 patients, three of which were novel: c.466_467dupAT, p.Leu157SerTer2; c.4540-1G>C; c.878delC, p.Met293SerfsTer7. The most recurrent ABCA4 variant was c.5882G>A, p.Gly1961Glu detected in 10 unrelated patients. Patients with biallelic severe ABCA4 variants or biallelic loss of function variants had an earlier age of ascertainment (p = 0.024 and p = 0.008, respectively). The mean interval between the referral of patients from the ophthalmology clinic and the first visit with the medical geneticist was 13.8 days, and the mean time to receive genetic test results with posttest counseling was 6.9 months after the first visit.

This study serves as a representative example of how genetic testing and a multidisciplinary approach can contribute to management of inherited eye diseases. It also reports three novel ABCA4 variants in Turkish patients with Stargardt disease and describes genotype–phenotype correlations. However, conducting multicenter studies with larger sample sizes from Türkiye will be essential to broaden the spectrum of ABCA4 variants and enhance our understanding of genotype–phenotype relationships.