Reacción a "Some treatments approved for multiple sclerosis are not effective for certain forms of the disease, according to a study. "

This is a retrospective study with a national database that benefits from its consequent sample size but suffers from multiple methodological biases inherent to these records, which limits the extraction of reliable result considerablys.

Firstly, patients with at least two EDSS (Expanded Disability Status Scale) evaluations are included, which could lead to an underestimation of the effect in patients with few evaluations (specifically, those with only two evaluations, where it is impossible to assess if subsequent confirmation of the event is required). Secondly, the treatment group includes patients with at least one cycle of anti-CD20 antibodies, without specifying the number of cycles or the number of patients for each treatment duration. Thirdly, there are significant differences in most baseline characteristics, with younger and more aggressive patients in the treatment group, who had shorter follow-ups. This could bias this group towards a poorer response. Although they attempt to mitigate this with propensity score matching, this statistical technique has limitations (mainly that it matches patients based on variables handpicked by the researchers). Fourthly, most patients were treated with rituximab, without specifying the doses and frequency of administration (as it was off-label use). Fifthly, only variables with statistically significant results in the univariate analyses are included in the multivariate analysis, which is a statistical error because all variables that could plausibly have an effect should be included.

Therefore, although real-world studies are necessary as a complement to clinical trials, the significant limitations of this study cast doubt on its superiority over the demonstrated results of ocrelizumab in primary progressive multiple sclerosis (given that rituximab has not been formally tested in this disease).