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.