By David Tuller, DrPH
I have recently written about a trial of an intervention for functional motor disorder (FMD) that had null results for its primary outcome—physical function as rated by the SF-36. The study–“Specialist Physiotherapy for functional motor disorder in England and Scotland (Physio4FMD): a pragmatic, multicentre, phase 3 randomised controlled trial,” published by The Lancet Neurology—had some positive results on a secondary measure of symptom improvement called the Clinical Global Impression for Improvement (CGI-I).
The investigators have recently published a follow-up paper, “Cost Utility of Specialist Physiotherapy for Functional Motor Disorder (Physio4FMD),” in the journal Neurology Clinical Practice. In this new paper, they have suggested that the CGI-I, rather than the SF-36, should have been their trial’s primary outcome. In making this argument, the investigators have misrepresented an earlier paper, even though some of them were co-authors on both.
I have written to Neurology Clinical Practice seeking a correction. The letter is below.
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Dear Editor:
A recent paper, “Cost Utility of Specialist Physiotherapy for Functional Motor Disorder (Physio4FMD)” [1], from Hunter et al., included a substantive error. The paper is a follow-up to “Specialist Physiotherapy for functional motor disorder in England and Scotland (Physio4FMD): a pragmatic, multicentre, phase 3 randomised controlled trial” [2], from Nielsen et al., published last June by The Lancet Neurology. (I have cc’d the lead authors of both papers.)
The Physio4FMD trial had null results for its primary outcome, the physical function subscale of the SF-36. However, it had positive results for one of its secondary outcomes, the Clinical Global Impression of Improvement (CGI-I).
In Hunter et al., the Physio4FMD investigators argue that this secondary outcome would have been a better primary outcome for their trial. They write: “It is notable that consensus recommendations for outcome measures in FND (published after this trial was planned) have recommended the patient-reported Clinical Global Impression of Improvement as the primary outcome measure in trials of interventions in FND.”
The reference for this statement is “Outcome measurement in functional neurological disorder: a systematic review and recommendations,” from Pick et al. [3], published in 2020 in the Journal of Neurology, Neurosurgery and Psychiatry. However, the statement in Hunter et al. about these recommendations is not true–Pick et al. did not recommend the CGI-I as the de facto “primary outcome measure” in intervention trials for FND.
Rather, Pick et al. listed the CGI-I as the preferred option for one specific “outcome domain” identified as “core FND symptoms.” And “core FND symptoms” was just one of several outcome domains highlighted in Pick et al. For the outcome domain called “life impact,” for example, the SF-36 was the main instrument recommended. In other words, contrary to the claim made in Hunter et al., Pick et al. did not identify one outcome measure as the best overall choice for FND intervention trials.
With this misrepresentation, Hunter et al. are implying that the SF-36 was the wrong primary outcome for their specialist physiotherapy trial–even though the investigators have promoted it for years as the most appropriate measure for assessing their FMD intervention. It is understandable that they would now want to downplay the importance and relevance of the SF-36, given that it yielded null results. However, Hunter et al.’s inaccurate statement about Pick et al.’s recommendations is certainly surprising, since there is some overlap in authorship between the two papers.
Whatever the source of this error, a correction is indicated.
Best–David T.
David Tuller, DrPH
Senior Fellow in Public Health and Journalism
Center for Global Public Health
School of Public Health
University of California, Berkeley
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[1] Hunter RM, Nielsen G, Le Novere M, et al. Cost utility of specialist physiotherapy for functional motor disorder (physio4FMD): economic analysis of a prag- matic randomized controlled trial. Neurol Clin Pract. 2025;15(3):e200465.
[2] Nielsen G, Stone J, Lee TC, et al.; Physio4FMD study group. Specialist physiotherapy for functional motor disorder in England and Scotland (Physio4FMD): a pragmatic, multicentre, phase 3 randomised controlled trial. Lancet Neurol. 2024;23(7):675-686
[3] Pick S, Anderson DG, Asadi-Pooya AA, et al. Outcome measurement in functional neurological disorder: a systematic review and recommendations. J Neurol Neurosurg Psychiatry. 2020;91(6):638-649.