The sample was based on patients whom had visited the Department of Dermatology in Turku University Hospital, Finland, between 1 October 2009 and 30 September 2010. They were all diagnosed to have Ps or PsA. In the Finnish health care system, patients with mild level Ps are treated at primary health care settings and only moderate-to-severe cases are referred to tertiary level hospital for further treatment. A total of 498 patients attended the clinic during the study period (428 had Ps and 70 had PsA). The patients were sent a questionnaire by mail. A total of 262 patients completed the questionnaire (52.6% of the total study sample). Patients with Ps or PsA participated equally .
Compliance with Ethics
The ethical committee of The Hospital District of Southwest Finland approved the study. The patients received a written description of the sampling procedure and study purpose, as well as the planned use and storage of the information they were to provide. The patients were asked to give a written consent to use their medical records for the study.
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 and 2008. Informed consent was obtained from all patients for being included in the study.
Socio-demographic background was collected with the questionnaire. The questions included gender, age, home municipality, number of persons living in the same household, income level and disease duration.
Out of the 262 patients who completed the questionnaire, 26 patients did not give written consent for the right to use their medical records. Clinical information was collected from the 236 patients’ medical records who gave consent, for the same time period that was covered in the questionnaire data. The information consisted of Psoriasis Area Severity Index (PASI), Dermatology Life Quality Index (DLQI), the diagnosis [ICD-10 (International Statistical Classification of Diseases and Related Health Problems)] and whether a patient had received UV-phototherapy during the study period. PASI describes the patient’s Ps severity and area, and the PASI values rise with increasing severity. PASI values are based on a scale from 0 to 72. Higher DLQI values represent a poor quality of life. DLQI values are based on a scale from 0 to 30. Laboratory costs were collected with a separate retrieval from the hospital’s patient records. They consisted of all the tests (not only monitoring) ordered by the dermatological clinic during the study period. Laboratory costs were from the whole study period and they could not be linked to a specific medication causally.
The Finnish Social Insurance Institution (FSII) reimburses part of a patient’s medicine expenses. In practice, all Finnish Ps patients receive reimbursements for all their Ps-related medications and emollients no matter who prescribes the medications. FSII provided data of all Ps-related medication purchases of the study patients who had given consent. Ps-related medication in this study comprised all biologic medications (including adalimumab, etanercept, infliximab, and ustekinumab), traditional systemic medications (including methotrexate, acitretin, and ciclosporin), topical drugs (including vitamin-D analogs, corticosteroid creams and combinations of these), leflunomide, topical fungal medicine, antihistamines and emollients. All purchases during the study period between 1 October 2009 and 30 September 2010 were recorded. FSII records of each purchase contained the total cost of the medication/emollient and the ATC-code (Anatomical Therapeutic Chemical Classification) of the purchase as well as the amount of packages purchased. ATC-codes were used to identify each drug. Drugs were clustered based on their active ingredients regardless of their brand names.
To analyze how many different types of treatments each patient used, treatment options were formed as following. All topical medications (not including emollients) were pooled as one treatment option. Traditional systemic medications (methotrexate, acitretin, and cyclosporine) were analyzed separately and each of them formed one treatment option. All biological medications formed one treatment option. They were pooled because of the low number of patients using them. UV-phototherapy was considered as one treatment option. Emollients, fungal medicines, antihistamines and other medications, which might have been used as supportive medications, were not considered as a separate treatment option. However, these medications were included for the total cost computations of medications.
The total cost of the drugs was used as the societal cost in all calculations without any reimbursement deductions. All medication costs were analyzed for the annual cost of medications per patient. Only the drugs in each treatment option were included for the cost calculations, when analyzing the costs of different treatment options. UV-phototherapy’s costs were not considered in any of the cost analyses.
In the analyses of the subgroup with PASI and DLQI values, all patients without recorded PASI or DLQI values were excluded. If several PASI or DLQI values were recorded for a patient during the study period, the arithmetic mean values were computed and used. When analyzing the subgroups with recorded PASI values, patients were divided by the median value into more severe (PASI > 5.5, n = 37) and less severe psoriasis (PASI ≤ 5.5, n = 35). The statistical evaluation of the data was based on Chi-square test for proportions and Student’s t test for means. The distribution of the DLQI values was skewed and to account for this, a Spearman’s non-parametric correlation was used.