Methodological considerations on immunoadsorption versus sham treatment for post-COVID syndrome

We read the paper by Marco Stortz et al.1 which is published in the Journal of the Lancet Regional Health - Europe in June 2026 with great interest. The authors aimed to determine whether autoantibody depletion by immunoadsorption is effective to reduce the symptom burden of patients with post-Covid syndrome, with a cross-over study. Although the results of the study are very interesting, however, it seems that several statistical and methodological issues should be considered when interpreting the results.