Effectiveness and cost-effectiveness of salicylic acid and cryotherapy for cutaneous warts: an economic decision model

Objectives: To estimate the costs of commonly usedtreatments for cutaneous warts, as well as their healthbenefits and risk. To create an economic decision modelto evaluate the cost-effectiveness of these treatments,and, as a result, assess whether a randomised controlledtrial (RCT) would be feasible and cost-effective.Data sources: Focus groups, structured interviewsand observation of practice. Postal survey sent to 723patients. A recently updated Cochrane systematicreview and published cost and prescribing data.Review methods: Primary and secondary datacollection methods were used to inform thedevelopment of an economic decision model. Data fromthe postal survey provided estimates of theeffectiveness of wart treatments in a primary caresetting. These estimates were compared with outcomesreported in the Cochrane review of wart treatment,which were largely obtained from RCTs conducted insecondary care. A decision model was developedincluding a variety of over-the-counter (OTC) and GPprescribedtreatments. The model simulated 10,000patients and adopted a societal perspective.Results: OTC treatments were used by a substantialnumber of patients (57%) before attending the GPsurgery. By far the most commonly used OTCpreparation was salicylic acid (SA). The results of theeconomic model suggested that of the treatmentsprescribed by a GP, the most cost-effective treatmentwas SA, with an incremental cost-effectiveness ratio(ICER) of 2.20 £/% cured. The ICERs for cryotherapyvaried widely (from 1.95 to 7.06 £/% cured) dependingon the frequency of applications and the mode ofdelivery. The most cost-effective mode of delivery wasthrough nurse-led cryotherapy clinics (ICER =1.95 £/% cured) and this could be a cost-effectivealternative to GP-prescribed SA. Overall, the OTCtherapies were the most cost-effective treatmentoptions. ICERs ranged from 0.22 £/% cured for OTCduct tape and 0.76 £/% cured for OTC cryotherapy to1.12 £/% cured for OTC SA. However, evidence insupport of OTC duct tape and OTC cryotherapy isvery limited. Side-effects were commonly reported forboth SA and cryotherapy, particularly a burningsensation, pain and blistering.Conclusions: Cryotherapy delivered by a doctor is anexpensive option for the treatment of warts in primarycare. Alternative options such as GP-prescribed SA andnurse-led cryotherapy clinics provide more costeffectivealternatives, but are still expensive comparedwith self-treatment. Given the minor nature of mostcutaneous warts, coupled with the fact that themajority spontaneously resolve in time, it may beconcluded that a shift towards self-treatment iswarranted. Although both duct tape and OTCcryotherapy appear promising new self-treatmentoptions from both a cost and an effectivenessperspective, more research is required to confirm theefficacy of these two methods of wart treatment. Ifthese treatments are shown to be as cost-effective asor more cost-effective than conventional treatments,then a shift in service delivery away from primary caretowards more OTC treatment is likely. A publicawareness campaign would be useful to educatepatients about the self-limiting nature of warts and thepossible alternative OTC treatment options available.Two future RCTs are recommended for consideration:a trial of SA compared with nurse-led cryotherapy inprimary care, and a trial of home treatments. Greaterunderstanding of the efficacy of these home treatmentswill give doctors a wider choice of treatment options,and may help to reduce the overall demand forcryotherapy in primary care