A Comprehensive Conceptual Model of the Experience of Chronic Itch in Adults

Abstract

Background: Itch is common and often debilitating. Itch is best assessed by self-report, often using patient-reported outcome measures (PROMs). Current PROMs for itch are limited and may not capture its full impact on quality of life (QOL).

Objective: We sought to develop a comprehensive conceptual model of itch to improve the understanding of itch for clinicians and to serve as a framework for development of efficient and valid PROMs of itch.

Methods: Using mixed methods, including systematic review (n = 491 articles), semi-structured interviews (n = 33 adults with chronic itch with multiple etiologies), and grounded theory using a constant comparative approach, we developed a conceptual model of itch.

Results: We found the Wilson and Cleary model to be a reasonable framework for organizing our findings. It includes five primary components: biological and physiological variables, symptom status, functional status, general health perceptions, and QOL. We propose a causal relationship beginning with the biological and physiological driving factors, with direct and indirect impacts of itch and its sequelae, including pain and sleep disturbance. These can impair function, lead to task avoidance, stigma, social life and relationship problems, emotional disturbances, and treatment burden. Together, these sequelae alter one's perceptions of health, QOL, and treatment response.

Conclusions: Our conceptual model demonstrates the profound patient-burden of itch and identifies unmet needs in the evaluation and management of itch.

Figure 1.

Itch-related domains identified by the expert panel, selective coding and constant comparative methods, and final bins.

Figure 2.

Conceptual model of itch. The five primary components of the Wilson and Cleary model are color coded: 1) biological and physiological variables , 2) symptom status including itch, scratch, pain and sleep disturbance , 3) functional status including functional limitations and task avoidance , 4) general health perceptions , and 5) health related quality of life . Additional itch-specific modifications of the model include stigma, social life and relationship problems, emotional disturbances, treatment burden and treatment response. Each of these steps in the model are potentially modified characteristics of the individual including activity motivation, emotional response to itch and baseline vitality and characteristics of the environment including climate, irritants, stressors and occupation .