Repeat survey of minimal clinically important difference:
Two surveys that were originally carried out for the PITCH pilot study8were repeated in order to re-evaluate their findings in current times. These surveys were created to determine the minimal clinically important difference (MCID) in itch score. The two surveys (one designed for women and one designed for clinicians) were completed using the online survey platform SurveyMonkey. The survey for clinicians was disseminated by the authors by email, via mailing lists of local and national obstetric medicine groups, and by Twitter and Facebook. The survey for women was disseminated by ICP Support, the patient support charity, through their social media channels.
Each survey asked two questions. The first question directly replicated a question in the original survey. Women and clinicians were told that the mean baseline itch score on a visual analogue scale of 0 to 100 mm was 60 mm. They were then asked to identify from a choice of distances on the scale, what size reduction in itch score they considered clinically meaningful. The second question asked the participant to identify the proportion of women who would need to change from itching so severe that they were unable to sleep through the night, to being able to sleep through the night, before they would consider taking or prescribing a drug. The full questions can be found in Appendix S2. Each survey also asked questions about basic demographics. The survey for women asked whether they had personal experience of ICP.
Basic demographics for both clinicians and women were calculated. Only women with prior experience with ICP were included in the analysis. The median value and interquartile range for each question in each survey was calculated. Responses were compared between women with and without prior experience of ICP.
All calculations in this secondary analysis were performed in Stata version 17 and replicated in R. All graphical outputs were created in R.