A review of how pain is measured in painful skin conditions and rheumatoid arthritis studies, to determine pain measurement in future hidradenitis suppurativa trials

Hidradenitis suppurativa (HS) is an inﬂammatory skin condition that causes boils, abscesses and skin tunnels in areas where there are creases in the skin. Pain is the most common symptom experienced by people with HS. This review aims to help the HIdradenitis SuppuraTiva cORe outcomes set International Collaboration (HISTORIC) group (a group of HS experts and patients with HS) identify the best method to measure pain in HS clinical trials. We looked at how researchers have measured pain in past clinical trials involving painful skin conditions (PSC, including HS) and rheumatoid arthritis (RA) with a focus on the pain numeric rating scale (NRS) and visual analogue scale (VAS). We found that most PSC trials did indeed use the pain NRS and the VAS tools. However, there was wide variation in how pain NRS and VAS data were collected (frequency, average pain intensity versus maximum pain intensity, recall window) in both PSC and RA trials. In addition, most trials used the mean difference (difference between average values in two groups) and only a few reported the results as the percentage of patients reaching a desirable state (for example, no pain or tolerable pain), which may be a better measure. These differences present a challenge when comparing the results of trials. In conclusion, our review showed there is wide variation in how pain is measured and reported in PSC and RA clinical trials. The information in this study will help our efforts to reach agreement on how best to measure pain in future HS trials.