Abstract
There is a need for simple, practical, and reliable measurement instruments for use in clinical trials, registries, and clinical practice to assess psoriasis severity and the change in symptoms with treatment. The Psoriasis Area and Severity Index (PASI) is the standard measure of psoriasis used in clinical trials, but it is rarely used in clinical practice and it is not readily used in clinical registries because of its complexity. The Physician Static Global Assessment score is a simpler measure also used in clinical trials and less frequently in registries and practice, but like the PASI, it requires some degree of experience to score. The Psoriasis Symptom Inventory (PSI) was developed as a simple measure to enable patients to self-score psoriasis severity. It has been demonstrated to be reliable and discriminative, and it correlated with the PASI score in a psoriasis clinical trial. It also was recently validated to assess psoriasis in a psoriatic arthritis (PsA) clinical trial. The PSI may be a useful and practical measure of psoriasis severity in psoriasis and PsA clinical trials, registries, and in clinical practice.
The Psoriasis Symptom Inventory (PSI) is an 8-item patient-reported outcome (PRO) measure that assesses the severity of psoriasis signs and symptoms1,2. The PSI was developed through contributions from literature review, expert clinicians, patient focus groups, and interviews with individual patients, resulting in a “saturation” of concepts regarding psoriasis signs and symptoms. The 8 questions address itching, redness, scaling, burning, stinging, cracking, flaking, and pain, with response categories of not present, mild, moderate, severe, and very severe. Wording and recall period appropriateness, comprehension, and item interpretation were confirmed through individual patient cognitive interviews. The measure can be used with either a 24-h recall period (for clinical trials) or a 7-day recall (for clinical practice).
In a brodalumab phase 2 trial in psoriasis, the PSI results closely mirrored those of the PASI (Figures 1–3). It demonstrated content, convergent, discriminant, and known groups validity, unidimensionality, and reliability, and was responsive and able to detect change in psoriasis severity (Table 1)3,4.
In a brodalumab phase 2 trial in PsA, the PSI recorded rapid and significant change in psoriasis5, and again demonstrated content, convergent, discriminant, and known groups validity, unidimensionality, and reliability, and ability to detect change (Table 2)5,6.
Currently, phase 3 trials of brodalumab are being conducted in which both the PASI and PSI are being measured to establish the correlation of these 2 instruments in patients with PsA.
It appears that the PSI can be a reliable, simple, and practical PRO to measure psoriasis severity in clinical trials, registries, and practice.
Acknowledgment
I thank Alex Mutebi, PhD, for editorial support.
Footnotes
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The Psoriasis Symptom Inventory (PSI) was developed collaboratively by Amgen Inc. and AstraZeneca/Medimmune with the involvement of expert clinicians and measurement experts. Amgen Inc. provided editorial support.