Background: In Huntington disease, the accurate determination of age-at-onset is critical to identify modifiers and therapies that aim to delay it.
Methods: Retrospective data from the European Huntington’s Disease Network’s REGISTRY. Data (age, gender, CAG repeat length, parent affected, and Unified Huntington’s Disease Rating Scale motor score, total functional capacity) from at least three visits in 423 REGISTRY participants were included. Data based extrapolations of individual age-at-onset using generalized linear mixed models based on individual slopes of motor score or total functional capacity, and predictions using the Langbehn, or Ranen formula, were compared with clinicians’ estimates.
Results: Concordance was best for the calculated onset using the REGISTRY UHDRS longitudinal motor scores. For total functional capacity, the investigator’s estimate was 4 years before the data derived age-at-onset. The concordance of predictions of probability of age-at-onset was ±20 years (difference in 25%tile).
Conclusions: Estimating or predicting age-at-onset in Huntington disease may be inaccurate. It can be useful to 1) add in the manifest population motor score regression derived age-at-onset as additional motor onset and 2) add total functional capacity regression derived age-at-onset for the onset of functional impact of Huntington disease when patients are in mid- to late-stage.