The Psoriasis Symptoms and Signs Diary (PSSD), a patient-reported instrument that assesses severity of 6 psoriasis symptoms, has strong psychometric properties and effectively differentiates clinical response to active treatments in clinical trials, according to a study published in the Journal of Dermatological Treatment.
Although psoriasis symptoms are best assessed by patients, current assessments of psoriasis severity conducted by clinicians do not take patient perspectives into account. Therefore, there is a need for valid, reliable instruments that consider patient-reported symptoms in psoriasis.
Researchers derived Psoriasis Symptoms and Signs Diary (PSSD) symptoms and signs summary scores (0 to 100) based on individual item scores (0 to 10; absent to worst imaginable). They then conducted analyses (using Psoriasis Area and Severity Index [PASI], Investigator’s Global Assessment [IGA], and Dermatology Life Quality Index [DLQI] data from the NAVIGATE trial of patients with moderate to severe psoriasis) to further validate the PSSD (7-day recall version) and establish criteria for clinically meaningful improvements.
Findings showed that mean PSSD symptoms and signs summary scores at baseline were 50.6 and 60.7, respectively, with no major floor (score of 0) or ceiling (maximum score) effects.
PSSD scores and changes in PSSD scores were highly correlated with IGA, PASI, and DLQL scores (most Spearman’s correlation r’s ≥0.4; all P <.001).
An improvement of 2-grade in IGA or an improvement of 75% to <90% in PASI was associated with clinically meaningful improvements of greater ≥40 points in PSSD summary scores and ≥3 to 5 points in individual score items.
“Our findings confirm previous validation results that the PSSD instrument possesses strong pscyhometric properties and is suitable for use as a measure of psoriasis severity in clinical studies of patients with moderate-to-severe psoriasis,” the researchers wrote.
“The identification of criteria for CMIs [cell-mediated immune responses] in PSSD summary and individual item scores will provide useful interpretation guidelines for measuring the effect of treatment on symptoms and signs of psoriasis,” they concluded.
Armstrong A, Puig L, Langley R ,et al. Validation of psychosometric properties and development of response criteria for the Psoriasis Symptoms and Signs Diary (PSSD): results from a phase III clinical trial [published online September 8, 2017]. J Dermatolog Treat. doi:10.1080/09546634.2017.1364694