Validation of the German Pruritus Questionnaire for the systematic assessment of chronic pruritus

Background: Chronic pruritus is a clinically heterogeneous symptom that manifests itself with varying duration, intensity, or quality. To date, there is no validated German-language instrument that systematically assesses the relevant parameters. With the support of the Pruritus Research Working Group (Arbeitsgemeinschaft Pruritusforschung, AGP), a questionnaire for the assessment of chronic pruritus (AGP questionnaire) was developed in 2008. The subsequently revised instrument, now called the German Pruritus Questionnaire, records pruritus-specific parameters such as localization, course, intensity and quality, anamnestic data on the general state of health, sociodemographic data, quality of life, and coping methods. It is to be validated in the study presented here. Patients and methods: The questionnaire was used in 366 patients with chronic pruritus of different etiologies from Germany (University Hospitals Heidelberg, Münster, Mainz, Erlangen, Giessen, private practice Bad Bentheim, TU Munich, Wiesbaden Kidney Center), Austria (Graz University Hospital) and Switzerland (Aarau Cantonal Hospital). Results: The reliability for repeated completion (retest reliability) with regard to localization, first occurrence, and concomitant diseases showed high values for Cohen's kappa (> 0.8). The data on the retest reliability of the pruritus characteristics showed lower values (< 0.7). With regard to the measurability of practically relevant changes (change sensitivity), medium to strong effect sizes were found (0.09–0.19). A statistically significant differentiation of the pruritus etiologies based on the recorded parameters was not possible. Conclusions: The German Pruritus Questionnaire allows a comprehensive and structured recording of patient- and clinician-reported, relevant dimensions of chronic pruritus of different etiologies. Further adaptation and development are planned.