Severity stages of chronic nodular prurigo: analysis of associated itch intensity and quality of life impairment

Introduction: Chronic nodular prurigo (CNPG) is a pruritic neuroinflammatory skin disease characterized by the presence of multiple pruriginous nodules. Previous psychometric analyzes showed the presence of moderate to severe pruritus and a considerable impairment of quality of life. A detailed study of these parameters in relation to the severity of the disease defined by the number of lesions is lacking. Methods: A total of 131 adult patients with CNPG were included. The number of pruriginous lesions and disease stage was determined by using the Prurigo Activity and Severity (PAS) scale and the prurigo-specific Investigator’s Global Assessment (IGA) scale. Patient-reported outcomes comprised pruritus intensity (worst itch intensity of the previous 24 h using the numerical rating scale; WI-NRS/24 h) and the impairment of quality of life (ItchyQol, Dermatology Life Quality Index; DLQI). Results: The counted and estimated number of pruriginous nodules correlated strongly with each other (r=0.82; P<0.001), moderately with the WI-NRS/24 h (counted number: r=0.44, P<0.001; estimated number: r=0.45, P<0.001) and with the DLQI score (counted number: r=0.40, P<0.001; estimated number: r=0.38, P<0.001). The severity groups of the CNPG, as defined by the IGA scale, correlated strongly with the WINRS/24 h and DLQI scores. With increasing severity of CNPG, increasing pruritus intensity and DLQI/ItchyQoL scores were recorded. Conclusion: The correlation between objective (disease stage) and subjective (itch intensity, quality of life) CNPG disease parameters argues for a representative disease severity characterization via physician assessments using either PAS or IGA.