Martin Metz, MD

Credit: Institute of Allergology, Charité–Universitätsmedizin Berlin

A qualitative, 5-item assessment tool known as the Prurigo Control Test (PCT) is newly-developed and validated for assessment of disease control among patients with chronic prurigo (including prurigo nodularis), according to recent findings.¹

This new study in which the PCT was validated may represent the very first patient-reported outcome measure designed for disease control determination, and its use in the future could help clinicians develop their treatment decisions for chronic prurigo patients.

This new research was led by Martin Metz, MD, from the Institute of Allergology, Charité–Universitätsmedizin Berlin at the Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin in Germany. Metz and colleagues noted that the difficulties with itch and other hindrances for chronic prurigo patients represent severe challenges that warrant further solutions.²

“To address this unmet need, we developed a novel, retrospective PROM, the Prurigo Control Test (PCT), for CPG to assess disease control in patients and quantify and monitor disease control,” Metz and colleagues wrote. “The development process aimed to generate a straightforward, short PROM that is easy to administer, complete, and evaluate.”

Background and Findings

The investigators followed existing recommendations for patient-reported outcome measure development, using this qualitative research to validate the PCT assessment tool. The assessment tool underwent several phases of generation of its items, reduction, and selection.

After they established the conceptual framework using an expert working group, the team carried out several semistructured interviews with 19 individuals with diagnoses of chronic prurigo. A single trained interviewer, well-versed in disease, conducted the surveys.

Those surveyed were asked about their personal experiences with the condition, covering what most troubled them about it, exploring the effects on their life quality, and pointing out pertinent questions for an assessment of their current disease control. After this, the investigators’ inquiries covered such aspects as signs and symptoms of disease, limitations in patients’ daily activities, sleep quality, influence on physical performance and mental health, social interaction impacts, and expectations regarding treatments.

This was then followed by assessments designed by the investigators for maintenance of internal consistency, convergent validity, test-retest reliability, screening accuracy, known-group validity, and banding. At first, the team had 69 possible PCT items in the phase in which items were generated.

Through the research team’s use of inter-item correlation, impact analysis, and reviews of content validity, a final set of 5 PCT items was established in the research. The team’s validation research was carried out within 2 expert centers found in Germany, with their information analyzed from February 2017 - November 2019.

The investigators ended up with a 5-item PCT. There was a recall period of 2 weeks, and a cutoff value of 10 points or higher was shown to be helpful for distinguishing those with well-controlled as opposed to poorly controlled chronic pain issues.

There ended up being 95 subjects considered by the research team in their validation analysis. They found the median age to be 63 years, with a range of 19-87.

The investigators also noted that 53% of the subjects were identified as women and the median disease duration was shown to be 72 months. The team’s validation investigation showed commendable internal consistency reliability as well as a notable convergent validity level.

Overall, the research team found the assessment tool to have robust known-group validity, with effective distinguishment of chronic prurigo patients with varying levels of disease control. They also found that there was high test-retest reliability, noting an intraclass correlation coefficient of 0.94 that suggested exceptional reproducibility.

“Results of this qualitative study show that the PCT is, to our knowledge, the first tool to assess disease control in patients with CPG,” they wrote. “Its retrospective approach, brevity, and simple scoring likely make the PCT suitable for clinical practice and trials.”

References

1. ^{Metz M, Zeidler C, Hawro T, et al. Development and Validation of a Patient-Reported Outcome Measure to Assess Disease Control in Chronic Prurigo. JAMA Dermatol. Published online January 17, 2024. doi:10.1001/jamadermatol.2023.5519.}
2. ^{Todberg T, Zachariae C, Skov L. Treatment and burden of disease in a cohort of patients with prurigo nodularis: a survey-based study. Acta Derm Venereol. 2020;100(8):adv00119. doi:10.2340/00015555-3471.}