Healthcare delay in neurogenetic disorders of adult onset and the role of predictive genetic testing.

Healthcare delay (HCDe) is an important but not well-known issue in genetic disorders, especially in tandem nucleotide repeat expansion diseases (TNRED). We aimed to investigate it and determine whether predictive genetic testing (PGT) and other factors may impact HCDe. A retrospective review was performed on electronic files of symptomatic and pre-symptomatic consultants (SC and PSC) by the time of their first evaluation, from TNRED families followed from 1998 to 2023. HCDe was the difference between ages at onset of symptoms (AO) and at start of healthcare for these symptoms in SC and PSC. Age, diagnosis, year of diagnosis, sex, AO, residence, schooling, index cases, and previous PGT were analyzed. Of the 1,100 subjects reviewed, 811 and 101 were SC and PSC carriers of Huntington disease, Huntington disease-like 2, spinocerebellar ataxia type 2, 3, 6, 7, or 10, or Friedreich ataxia. Their median (IQR) HCDe was 5 (6) years and did not differ across diseases. Over the years, the number of annual PSC diagnoses became similar to that of SC. Better schooling and recurrent familial cases were associated with shorter HCDe, but the strongest effect on HCDe was related to PGT: in 33 PSC who converted and came to healthcare, HCDe was of 1 year (p < 0.0001, MW). HCDe was large in all TNRED studied. Parameters related to better access to information, especially PGT, improved HCDe. As molecular diagnoses become more frequent in PSC, we expect that HCDe will be reduced in the future.