Eight Korean dermatologists who specialize in psoriasis completed the questionnaire. All of the participants gathered at the same location for a consensus conference. The participants answered 11 questions from the European consensus on psoriasis treatment goals using electronic voting software installed on iPads (Apple Inc., Cupertino, CA, USA). All participants voted on the same question simultaneously, and the results from the voting were projected on a screen immediately after the participants had answered the question. All of the participants then discussed their opinions about the displayed result. The Delphi technique, which was used to reach consensus from participants who had different views on the same questions in Europe, was not used in this consensus conference because the number of psoriasis specialists in Korea is too small for this technique to be effective and there were time constraints. There were four categories of questions about psoriasis treatment, namely, the classification of psoriasis severity, the definitions of the induction and maintenance phases for the systemic treatment of psoriasis, the definitions of treatment responses during the induction phase, and the definitions of treatment responses during the maintenance phase. The study was exempt from the institutional review board at the Seoul National University Bundang Hospital (No. 406-53-903).

The responses to the 11 questions from the European consensus conference were compared with the Korean responses. The proportions of positive answers were calculated, and the differences between the European and Korean consensuses were compared. Fisher's exact test for independent variables was performed on each question using SPSS Statistics 17.0 (SPSS Inc., Chicago, IL, USA). A p-value of less than 0.05 was considered to be statistically significant.

In contrast to the European consensus, which used the Delphi technique to obtain a strong consensus in the final results, the Korean consensus conference did not use a repetitive voting technique. Most of the consensus questionnaire responses showed relatively weak agreements compared with the European consensus. However, most of the areas of agreement did not differ from those in the European consensus, despite the small number of participants and not using the Delphi technique.

The participants were asked three questions to define the concept of psoriasis severity in the context of clinical practice in Korea. The classification of psoriasis into mild versus moderate-to-severe psoriasis to provide guidance in relation to treatment modalities was agreed to by 62.5% of the participants (Table 1). The explanation given for disagreement was that this classification does not reflect the effects of psoriasis on particular locations, including the face, nails, scalp, and genitalia, because even mild psoriasis in these areas can have significant impacts upon on the health-related quality of life (HRQoL). Two questions considered the subjective impact of psoriasis on HRQoL, which did not correlate with the doctors' assessments. These questions asked about the classifications of mild psoriasis with a high impact on HRQoL, and severe psoriasis with a low impact on HRQoL. The agreement for considering a low PASI/BSA with high DLQI to be moderate to severe psoriasis was 62.5%, but only 37.8% agreed that a high PASI/BSA with low DLQI could be classified as mild psoriasis. In response to the former question, it was stated that due to differences in psoriasis severity from Caucasians, the suggested cut-off value for the BSA, 10%, is not appropriate for Korean patients. The last question in this part of the questionnaire was the only one that showed a statistically significant difference compared with the European consensus. The major reason for the objection was that it is impossible to achieve improvements while using topical medications on patients who have clinically severe psoriasis, irrespective of how minimally psoriasis affects a patient's quality of life.

When using systemic treatments for moderate-to-severe psoriasis, it can take a long time to assess the efficacy of a particular medication. Categorizing the treatment period into an induction phase and a maintenance phase can be helpful for scheduling or changing medications (Table 2). Of the participants, 62.5% agreed to a definition of the induction period as 16~24 weeks. The main reason underlying the objections to this definition was that many psoriasis medications can achieve noteworthy improvements within 12 weeks. All of the participants agreed with the concept of induction and maintenance phases. Most of the participants agreed that there was a need for the concept of a maintenance period in systemic treatment.

The questions relating to the definitions of treatment responses during the induction phase generated total agreement among all of the participants (Table 3). The response to treatment during the induction phase can be assessed using the PASI score. The treatment can be considered effective if the PASI score improves by 75% or more. If the PASI score improves by 50% or less, the current medication can be considered ineffective. In relation to the question about a borderline response, which is defined as an improvement in the PASI score of more than 50% but less than 70%, 87.5% of the participants agreed that this should be re-evaluated using the DLQI score. The reason given for the disagreement was that the DLQI is currently not commonly used in routine clinical practice.

The responses to the questions about the maintenance phase were almost the same as those to the questions about the induction phase, with the only difference relating to the continuation of a regimen after a PASI reduction of 75% had been achieved during the maintenance period (Table 4). In contrast to the induction phase, doctors always confront the decision of when to reduce or stop a regimen during the maintenance phase. Not all of the participants could agree on the necessity to continue a maintenance regimen after improvements.