Understanding the clinical symptomatology of psoriasis is complex and the tools available to us have their limitations. A controversial starting point for this workshop was the question: ‘Why should we measure disease activity in psoriasis?’ Some of the reasons given by the participants included the following:
• To assist medical intervention decisions
• Medical documentation
• Treatment outcomes assessment (clinical trials)
• To assess comparative efficacy
• To assess placebo response
• Pharmacoeconomic evaluations/reimbursement
• Registries and epidemiology
In clinical trials, clearly some form of objective measure is required but, in clinical practice, is it relevant to the patient? Perhaps more important is the subjective view of the patient. Are they happy with their current therapy or not? However, the patient’s view of their psoriasis is almost universally focused on the skin pathology and avoids issues relating to comorbidities. Data is accumulating with respect to an association between comorbidities (metabolic syndrome and dyslipidemia, which can increase cardiovascular risk) and severe psoriasis. Therefore, reducing the Psoriasis Assessment and Severity Index (PASI; as a surrogate for disease severity) may be clinically important in that it may reduce the risk of adverse secondary outcomes. There are issues with interpretation of patients’ responses regarding ‘happiness with treatment’, since verbalization of concerns can be a problem for some individuals. The responses on the Dermatology Life Quality Index (DLQI) do not often reflect what the patient has said about their psoriasis and their general view or assessment regarding how well a treatment is working. A more systematic approach is needed to ascertain a clearer picture that can be analyzed with some level of validity.
An interesting discussion then ensued regarding the measurement tools available for assessing the severity of the skin problems associated with psoriasis. Many techniques have been used over the years, including PASI, body surface area, investigator global assessment, photographic records and associated image analysis techniques, disease history, symptoms measurements and more objective measures, such as ultrasound, blood-flow measurements and colorimetry. Symptoms such as itch, irritation and burning are frequent concerns for psoriasis patients in everyday life, and they are not included in PASI scores, yet they can lead to impaired quality of life (QoL). PASI scores are the most commonly reported measures of psoriasis severity, but there was general agreement that they are notoriously difficult to measure and determine accurately. Despite the research in the assessment of new measurement techniques for psoriasis severity, PASI remains the most widely used tool. The PASI involves measuring psoriatic lesions in four regions of the body (head, trunk, upper extremities and lower extremities) and, in each of these, assessing the lesions for redness, scaling and thickness with a total score of 0–72 thus being possible. A problem with this system is that the scale is not linear and that any score of more than ten probably represents moderate-to-severe psoriasis. Given that PASIs are difficult to measure, in clinical trials it is important to use trained observers to perform the task.
Quality of life is a key issue for patients with psoriasis, and measurement techniques include:
• Disease specific: Psoriasis Disability Index and Psoriasis QoL Index (PSORIQoL)
• Dermatology specific: DLQI and Skindex
• General: Short Form-36 and Euroqol
The DLQI is a very simple technique for estimating QoL and involves ten questions, each scoring between 0 and 3. The questionnaire takes approximately 2 min to complete and covers the most obvious ways that the disease affects them personally (itchiness, pain, embarrassment, daily activities, clothes, social life, sport, work, study, relationships, sexual difficulties and treatment). Total scores on the DLQI range between 0 and 30, and perhaps the most important thing to remember is that scores over ten signify that the psoriasis is having a large negative effect on the patient’s QoL.
Despite their problems, PASI (for disease severity) and DLQI (for QoL) are the two most frequently used measures for assessing the impact of psoriasis on the individual. Consequently, there is a large volume of historical (comparative) data with these measures available in the literature.
The question addressed in the workshop was: can we establish treatment goals that can be applied on a day-to-day basis to provide the best level of care for our patients? An interesting debate followed with the prevailing view that PASI-75 or higher (PASI-90 was suggested by a few participants) would be an appropriate treatment goal. In terms of a minimal goal, PASI-50 or higher was generally agreed upon. With regards to setting goals for DLQI as an indicator of QoL, the challenges are a little greater. Setting a DLQI of 0–1 may be very difficult to attain in patients whose QoL is severely impaired to start with. There was some discussion as to whether or not an absolute decrease in DLQI (e.g., by five points or more) may not be a better option but, for patients who start with high DLQIs, this may not be sufficient. How do the different biologic therapies compare when you assess their ability to achieve a treatment goal of PASI-75? Based on a literature review, infliximab 5 mg/kg (∼80%) was superior to etanercept 2 × 50 mg/week (50%), etanercept 2 × 25 mg/week (35%) and efalizumab (30%). Similar findings were noted when PASI-90 was the treatment goal. Interestingly, while there is generally no relationship between absolute PASI and absolute DLQI, in the European Infliximab for Psoriasis Efficacy and Safety Study (EXPRESS) there was a correlation between the improvement in DLQI and the reduction in PASI score. However, even when PASI was 0 (no skin problems), a DLQI of 0 was only reported in approximately 70% of patients. Based on these findings, achieving a DLQI of 0–1 is clearly a challenging treatment goal and probably equates to a PASI-90 or higher. Goals should also be considered for nail and joint problems in affected patients.
The timing of assessment measurement (i.e., when the drug produces its maximum effect) is also important and is different for the various treatment modalities: 10 weeks for infliximab, 12 weeks for most other biologics and 12–16 weeks for drugs such as methotrexate and acitretin. Furthermore, treatment goals should be checked every 4–8 weeks during therapy.
Practical implications
How is this information useful to dermatologists in everyday practice? Possibly the most important use is helping to define when the psoriasis is becoming severe and requires more aggressive therapy (the most likely option being intervention with systemic therapy). In this regard, the ‘Rule of 10s’ was suggested as a relatively simple method to achieve this (Box 1).
If the patient has any of these, then the disease can be considered moderate to severe. This technique has been adopted by a number of different groups and organizations as an appropriate indicator to initiate systemic or biologic therapy.
A more formal evaluation of the negative impact of psoriasis on the QoL of the patient in daily life may help with discussions concerning the possible initiation of systemic therapy or whether to admit to hospital or not, and it can also act as a record when difficult decisions are being made.
Ultimately, we must position ourselves so that we can better assess disease severity, which enables us to make more informed decisions and allows us to create treatment goals, which set standards to assess and improve patient outcomes and care.
Box 1. ‘Rule of 10s’.
Severe psoriasis = body surface area >10% or PASI >10 or DLQI >10.
Financial & competing interests disclosure
AY Finlay has had consultancies with or honoraria from Schering-Plough, Wyeth, Novartis, Pierre Fabre, Serono, 3M, Galderma, Abbott Laboratories and Pfizer. AY Finlay is joint copyright holder of the DLQI. Writing assistance was provided by Steve Clissold PhD (Content Ed Net), with funding by Schering-Plough, USA. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.
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