Measuring costs
SECONDARY
In keeping with an NHS perspective, all acne-related resource use data, including intervention, primary and secondary care visits, and prescription medication use, were collected for participants in both groups. Personal Social Services resource use was not collected, as patient and clinician contributors did not anticipate these being incurred by participants.Resource use data were collected via case report forms and participant questionnaires (see 
Resource use was valued using UK unit costs (£ Sterling) for the most current price year available at the start of analysis (financial year 2021) and identified from published sources.The intervention was costed as described in Intervention resource use as per standard treatment with spironolactone (base-case).* Assumes all patients escalated to two 50 mg tablets spironolactone at 6-week visit. Based on the data from the trail, this was the case for 182/184 (99%) in the spironolactone group at 6 weeks (question response rate 184/202 in spironolactone group).† Existing evidence and expert opinion recommend ongoing blood monitoring for women aged >45 years, or those with relevant comorbidities or on treatments with increased risk. As the latter two were not included in the trial, it is not possible to estimate the proportion of such patients that might receive spironolactone and need blood test monitoring. 6/201 (30%) patients in the spironolactone arm of the trial were aged >45 years. GP, General Practitioner.Acne-related resource use data related to visits to community-based healthcare professionals (HCP), visits to hospital out-patient and in-patient services (including accident and emergency) and prescribed medication costs were self-reported via participant questionnaires at all time points, including baseline for participants in both groups. When asked about medication use, participants were asked to report only what they had been prescribed since the previous follow-up visit. Unit costs for each visit-type were combined with this data to estimate the total community-based HCP visit costs and the total hospital contact costs. Participants were also asked for details of prescribed acne-related medication including type, strength and quantity. Unit costs for all medication typesThe mean (SD) cost per participant per intervention group was estimated for the 24-week treatment period, for each of the cost types described above and mean difference (95% CI) in NHS cost was estimated.