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Dermatologists recently have developed and validated several tools for assessing itch in plaque psoriasis, such as the Peak Pruritus-Numerical Rating Scale.
Historically, psoriasis has been considered a non-pruritic skin condition, which has contributed to a lack of standardized methods to evaluate itch in this disease state.
“A general agreement including pruritus as a measure of quantification of psoriasis severity has not been established so far; however, pruritus prevalence in psoriasis seems to be of interest, with a prevalence varying between 60% to 90% of cases,” wrote Silviu-Horia Morariu and colleagues in a paper published in Life. “Despite its relatively high prevalence, the available data regarding the clinical characteristics of itch in psoriasis remain limited.”
Given increasing interest in understanding how pruritis impacts patients with psoriasis, there have been several recent updates in the tools dermatologists are using to assess itch.
PP-NRS for Mild-to-Moderate Disease
The Peak Pruritus-Numerical Rating Scale (PP-NRS) has been validated in other dermatological diseases. In an article published in the International Journal of Dermatology, researchers used data from a phase 2b study to validate the PP-NRS in mild-to-moderate plaque psoriasis.
“Pruritus is a common, bothersome symptom for patients with mild-to-moderate plaque psoriasis, yet no validated scale assesses it in this patient population,” wrote Zoe D. Draelos, MD, and colleagues.
The participants completed the PP-NRS daily for the first two weeks after the study began, then subsequently only when returning for visits. Dr. Draelos and colleagues used correlation and regression analyses to determine the PP-NRS’s test-retest reliability, construct validity, ability to detect change, and meaningful within-patient change.
With an intraclass correlation coefficient of 0.86-0.89, the PP-NRS showed acceptable test-retest reliability.
“Known-group evidence demonstrated that PP-NRS scores could discriminate between different degrees of disease severity,” the authors reported.
The PP-NRS also demonstrated significant correlations with the Patient Global Assessment, Dermatology Life Quality Index (DLQI), and Psoriasis Symptom Inventory, further supporting its validity. In addition, changes in PP-NRS had a linear relationship with both Patient Global Assessment and Physician Global Assessment scores.
The researchers concluded that the PP-NRS is reliable in mild-to-moderate plaque psoriasis, with 2.8 considered a meaningful within-patient change.
A New Itch Questionnaire
In another recent paper, Morariu and colleagues from Romania created a comprehensive questionnaire to assess the prevalence and characteristics of itch in their patients. The questionnaire contains 48 total questions. It prompts patients about disease factors such as onset age, whether they underwent a skin biopsy, and whether psoriatic lesions are constant or dynamic, etc. Patients also indicated what types of treatments they received for their psoriasis and what comorbidities they had (Table).
The cross-sectional study included 163 patients aged 19 to 87 years (mean disease duration of 17.3 ±13.55 years), and 115 patients (70.55%) in the cohort reported itch. The statistical analysis showed significant differences between patients with and without pruritus in terms of higher Psoriasis Area and Severity Index (PASI) (P=0.003), DLQI (P<0.001), and BMI (P=0.03).
Questionnaire responses revealed that 94 patients described their itch as a crawling sensation, while others reported discomfort, burning, stinging, or pinching. Up to 40 patients reported additional symptoms, such as pain (23 patients) or sweating (17 patients) in the pruritic areas.
Pruritus appeared every other day for 86 patients (74.78%) and lasted for a few minutes (3.48 ± 1.25). Most patients (81.73%) localized itch in the areas affected by psoriasis, although 19 patients also reported it in non-lesional skin. The itch was intermittent in nature (95.65%) and tended to occur simultaneously with psoriasis lesions (60.86%).
Stress was the most significant factor exacerbating pruritus (76.52%). Other triggers included heat (9.56%), cold (6.96%), sweat (5.22%), and certain foods like spicy dishes or caffeine (4.34%). Pruritus was also more frequent during colder seasons such as winter (37.39%) and autumn (17.39%).
The researchers noted that their study was limited by its single-center design. In addition, the questionnaire was designed by experienced dermatologists but should be validated in future research.
“A better understanding of itch and its clinical features and integration into future psoriasis guidelines will guide physicians toward the best treatment of choice,” the study authors concluded. “This would, ultimately, benefit the patient.”
