Placebo Effect in Chronic Inflammatory Demyelinating Polyneuropathy: The PATH study and a systematic review.

Background and Aims The PATH study required subjects with chronic inflammatory demyelinating polyneuropathy (CIDP) to show dependency on immunoglobulin G (IgG) and then be restabilized on IgG before being randomized to placebo or one of two doses of subcutaneous immunoglobulin (SCIG). Nineteen of the 51 subjects (37%) randomized to placebo did not relapse over the next 24 weeks. This article explores the reasons for this effect. A post-hoc analysis of the PATH placebo group was undertaken. A literature search identified other placebo controlled CIDP trials for review and comparison. In PATH, subjects randomized to placebo who did not relapse were significantly older, had more severe disease, and took longer to deteriorate in the IgG dependency period compared with those who relapsed. Published trials in CIDP, whose primary endpoint was stability or deterioration, had a mean non-deterioration (placebo effect) of 43%, while trials with a primary endpoint of improvement had a placebo response of only 11%. Interpretation Placebo is an important variable in the design of CIDP trials. Trials designed to show clinical improvement will have a significantly lower effect of this phenomenon than those designed to show stability or deterioration. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

RCT Entities:   Population Interventions Outcomes