Psoriasis is a chronic, inflammatory, immune-mediated skin disease with genetic associations. It is characterized by sustained inflammation leading to uncontrolled keratinocyte proliferation and dysfunctional differentiation.1 Psoriasis has both a physical and psychological impact that results in diminished patient quality of life.2

It has been estimated that the incidence of psoriasis varies by age and geographic location.3 As a chronically remitting and relapsing disease, it requires long-term treatment with topical agents (corticosteroids, calcineurin inhibitors, vitamin D derivatives), which, depending on disease severity, comorbidities, and healthcare access, may or may not be combined with systemic therapies (methotrexate, cyclosporine, retinoids, biologic agents).1 Several clinical practice guidelines (CPGs) have been developed to reduce variability in treatment recommendations for psoriasis.4–6 CPGs are “systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances”.7 Their development is both costly and laborious, and potential benefits depend on the quality of the guidelines.8

Proper guideline implementation hinges on rigorous development methodology and strategies.9,10 Organizations such as the Institute of Medicine, the National Institute for Health and Clinical Excellence, the World Health Organization, the Scottish Intercollegiate Guidelines Network, and the Guidelines International Network provide useful resources for helping guideline developers produce higher-quality recommendations.11 Despite a growing body of resources, however, suboptimal CPG quality, poor adherence, and variability in recommendations remain a problem,10,12 hence the importance of assessing the methodology used for development. Tan et al.13 performed a critical appraisal of psoriasis CPGs published between 2006 and 2009. Since then, however, new guidelines have appeared while others have been updated. The aim of this study was to perform a systematic appraisal of the methodological quality of CPGs on the treatment of psoriasis published in the past decade using the Appraisal Guidelines Research and Evaluation II (AGREE II) tool.

CPGs are useful tools for bridging the gap between the growing number of scientific publications and daily clinical practice; they help physicians make decisions about their patients.47 Numerous guidelines have been published in the field of dermatology, but their quality must be assessed to ensure adequate implementation. In this study, we systematically appraised the quality of 19 CPGs on the treatment of psoriasis. Three-quarters of the CPGs included were classified as high quality and more than half were recommended for use in clinical practice. The quality rating contrasts with findings for CPGs on the treatment of other skin diseases, such as acne and dermatitis, which have been rated as low quality.48–50

The highest-scoring AGREE II domains in our study were scope and purpose and clarity of presentation. At the other end of the scale were applicability and editorial independence. Similar results were reported in a critical appraisal of 8 CPGs on the management of psoriasis vulgaris13 and quality assessments of CPGs on atopic dermatitis51 and acne.52 Low applicability scores have been attributed to limited discussion of organizational barriers and gaps between the formulation of recommendations and implementation processes.11,13 There would, therefore, appear to be certain discrepancies between the real-life applicability of CPGs and the evidence-based recommendations they include. As suggested in a study of CPGs on acne, appraisals might also be influenced by subjective judgments about implementation processes or adherence.52

In addition to evaluating the quality of the CGPs according to the different domains of the AGREE II tool, we classified CPGs as low- or high-quality using a scoring system that provides greater weight to rigor of development (Table 3). This system has been used in several studies53 and considers studies with an AGREE II score of 60% or higher to be of high quality. It is considered to be methodologically sound as the rigor of development domain has been found to have the strongest influence on overall assessment of guideline quality.54,55 Accordingly, assessments of overall quality and recommendation for use may not always be consistent with high- or low-quality ratings based on the cutoff score of 60%.36 The Italian guidelines on plaque psoriasis,36 for example, received a low overall score and were not recommended for use, but because they scored 60% or more in 4 domains, including rigor of development, they were classified as high-quality (Table 3).

Most of the CPGs were developed in high-income countries using rigorous guideline development methodologies. Lower AGREE scores have been reported for guidelines developed in low- and middle-income countries (e.g., Latin American countries).56 The applicability domain, with a mean score of 46.6%, was the lowest-scoring domain in our critical appraisal, supporting findings from other independent assessments, even of high-quality CPGs in the field of dermatology.57 Addressing the aspects covered in the applicability domain is important for the development of higher-quality CPGs, which should also consider the health care system in place in the target area and include recommendations that take into account variability in health care needs and accessibility. Most of the CPGs analyzed were developed in countries with largely government-run health care systems, financed by the state or society. Examples are etatist social health insurance programs and national health services. Other CPGs, however, were developed in countries with insurance-based systems (multiple insurers, social health insurance, and national health insurance) or private health systems, where health care regulation varies geographically, socially, and sectorially and where financing and service delivery lie mainly in the hands of for-profit providers (Table 2).

This study has several limitations. First, the evaluators found it difficult to distinguish between the scores of 3, 4, and 5 on the 7-item scale because the updated AGREE II tool only provides a clear definition for items 1 (strongly disagree) and 7 (strongly agree); the tool has been assessed several times since its development.14,15 Variations in interpretation constitute a potential source of reporting bias, although interrater agreement was high (ICC, 0.621). Second, even though we applied a comprehensive search strategy, with no language restrictions, we may have missed CPGs registered in databases for other languages or published by private organizations (e.g., a nonindexed CPG developed for a specific institutional purpose). Third, we did not include CPGs on psoriatic arthritis, which is an important treatment component in psoriasis.

Our study also has some strengths. First, we used a robust search strategy adapted to several databases and open to all languages to avoid language bias. Second, the critical appraisal was performed by an interdisciplinary team of dermatologists and methodologists to achieve a balance between methodological and clinical applicability issues. Third, we checked interrater agreement using a selection of the articles analyzed and statistically assessed interrater differences with the aim of improving agreement in the overall assessment. Fourth, we analyzed CPGs published between 2010 and 2020 to address improvements and new treatment options that have been made available for different types of psoriasis since the first critical appraisal of CPGs on psoriasis was published in 2010.13 Finally, we used the latest version of the AGREE II tool, which is a well-known and widely accepted methodological tool for assessing CPG quality.

Our updated search in August 2021 retrieved the National Psoriasis Foundation (NPF) guidelines on the management of psoriasis during the COVID-19 pandemic (versions 163 and 264). Although these guidelines did not meet the methodological criteria for inclusion, their content is highly relevant, as the NPF created a COVID-19 task force to produce guidance on prevention, clinical decision-making, and optimization of general measures in psoriasis patients undergoing treatment (phototherapy); the aim was to reduce the risk of SARS-CoV-2 infection. The guidelines include several important pandemic-related recommendations supported by strong evidence. First, patients without contraindications to vaccination should be administered an mRNA-based COVID-19 vaccine as soon as it becomes available while continuing to receive systemic treatment (oral or biologic agents) and decisions regarding changes to treatment regimens for the administration of the vaccine should be taken on a case-by-case basis. Second, patients should continue to receive the inactivated influenza virus. Third, patients without SARS-CoV-2 infection should continue to receive biologic or oral treatments for psoriasis. Fourth, psoriasis patients who become infected with SARS-CoV-2 should be managed using the same protocols as those applied to the general population, but their care should involve a multidisciplinary approach, with consultation of dermatologists, rheumatologists, and infectious disease specialists. Fifth, antimalarials and ivermectin are not recommended for the prevention of SARS-CoV-2 infection.

The updated CPGs published by Nast el al. in 202065 and 202166 provide additional recommendations on the use of new systemic therapies, with a focus on biologics (interleukin 17 and 23) that had been approved for the treatment of moderate to severe psoriasis vulgaris in Europe. These guidelines compared the clinical effectiveness of different biologics using network meta-analysis and formulated recommendations on the treatment of psoriasis in the context of the pandemic. Likewise, the updated British Association of Dermatologists guidelines on the use of biologic therapy for psoriasis published by Smith et al67 in 2020 recommend using new biologics that have already been licensed or are expected to be licensed for use in the United Kingdom, such as certolizumab pegol, ixekizumab, and tildrakizumab for adult and pediatric populations.

To summarize, most of the psoriasis CPGs analyzed in this critical appraisal can be considered high-quality guidelines, although we did detect shortcomings in the domains of applicability and editorial independence. Our findings also revealed continuing gaps in CPG development between high- and low-income countries. The applicability of CPGs needs to be improved. Guideline developers need to consider the target health care system(s) to ensure that the recommendations they include are viable and can be successfully implemented.

This study did not receive any funding from the public or private sector or any not-for-profit associations.

The authors declare that they have no conflicts of interest.