Questionnaire use depends on the study goal, target group and phase of the condition.

Assessment of questionnaires in research and clinical practice has become part of the daily routine, facilitated by the digital opportunities that allow patients to electronically fill out questionnaires in an easy, accessible way in a relatively short amount of time. Moreover, the overall methodological quality has largely improved during the last decade.

Frequently used questionnaires and assessment tools are usually characterized by high standards of reliability and internal and external validity. The choice of questionnaires therefore largely depends on the goal and content of the study and the related target population. Additionally, there are key differences in requests for assessment instruments in different research settings. For example, while a short questionnaire with relatively broad categories might be most useful as a screening and signal detection instrument in clinical practice in large epidemiological studies, a similar questionnaire might not be sensitive enough to use in a large randomized controlled trial to study small changes during new therapies in different subgroups of patients. A well‐known example is the EuroQol‐5D, which is the most frequently used and best validated scale for cost‐effectiveness analyses in skin disease and other conditions, although the sensitivity of the five items has been questioned in skin diseases.

Such differences in questionnaire use are also reflected in the present study in this issue of the BJD. Szabó et al. compare the Dermatology Life Quality Index (DLQI), DLQI‐Relevant and Skindex‐19. The DLQI is the most well‐known, easy‐to‐use and validated questionnaire in many countries, with extended norms for many skin conditions. It is most useful as an overall quality‐of‐life instrument to get an impression of the impact of the skin disease on daily life. On the other hand, Skindex‐19 might be more sensitive than the DLQI when it comes to describing specific psychological and social dimensions that might change during the course of the disease, for example in self‐management studies. This may also apply to other questionnaires that have been developed for specific purposes with regard to skin diseases, such as the measurement of itch–scratch problems (e.g. Impact of Chronic Skin Disease on Daily Life), stigmatization (e.g. Weight Self‐Stigma Questionnaire) or illness cognitions (e.g. Itch Cognition Questionnaire).

In the end, there is no one‐size‐fits‐all solution to the assessment of the various dimensions that are impacted by the effects of skin diseases. It all depends on the particular perspective of the given study. Further research will benefit from a more detailed and systematic description of the exact purpose and added value of specific questionnaires in particular fields where they would be most useful, along with an overview of which questionnaires might work for whom, in which conditions, and during which phase of the disease.

Author Contribution

Andrea W.M. Evers: Writing – original draft (lead); Writing – review & editing (lead).