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Original Investigation
July 7, 2021

Limitations of Using Questionnaires for Assessing the Prevalence of Psoriasis and Atopic Dermatitis Among Adults

Author Affiliations
  • 1Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
JAMA Dermatol. Published online July 7, 2021. doi:10.1001/jamadermatol.2021.2307
Key Points

Question  What is the test-retest accuracy of questionnaires on psoriasis and atopic dermatitis for measuring prevalence in an adult population?

Findings  This cohort study of 2333 participants who responded to a psoriasis questionnaire first in 2018 and again in 2020 found high agreement between their individual answers. However, the study found low agreement between the individual answers of 2312 participants who responded to an atopic dermatitis questionnaire in 2018 and again in 2020.

Meaning  Asking people about a history of psoriasis may be useful for assessing psoriasis prevalence, but a questionnaire does not appear to be a reliable method for assessing atopic dermatitis prevalence among adults.


Importance  Questionnaire studies are important for estimating the prevalence of psoriasis and atopic dermatitis; however, validity among the adult population remains an important concern.

Objective  To examine the test-retest accuracy of questionnaires for measuring psoriasis and atopic dermatitis prevalence in an adult population.

Design, Setting, and Participants  This nationwide population-based cohort study administered questionnaires on psoriasis and atopic dermatitis to the same 2333 and 2312 randomly selected adults (≥18 years) in Denmark, respectively, at 2 different time points from May 15, 2018, to November 20, 2020. Data were analyzed from January 10 to January 28, 2021. To reduce the risk of participation bias, potential respondents were given information on the research project only after agreeing to participate.

Exposures  Participants were asked identical questions on psoriasis and atopic dermatitis in 2018 and in 2020. Responses were linked at the individual-level.

Main Outcomes and Measures  The test-retest reliability (expressed by Cohen κ).

Results  The psoriasis questionnaire was completed by 2333 (mean [SD] age, 55.1 [16.2] years; 1338 [57.4%] women) participants in 2018 and in 2020. The atopic dermatitis questionnaire was completed by 2312 (mean [SD] age, 55.0 [16.2] years; 1326 [57.4%] women) participants in 2018 and in 2020. Among participants reporting a history of psoriasis, agreement between individual responses was high (κ = 0.7558); however, among those reporting a history of atopic dermatitis, agreement was low (κ = 0.4395). For psoriasis, prevalence changed from 7.8% to 8.0%; for atopic dermatitis, from 8.2% to 7.6%. Of participants who in 2018 reported dermatologist-diagnosed atopic dermatitis, 36.9% claimed in the 2020 questionnaire that they had never had atopic dermatitis. Analyses revealed substantial agreement for psoriasis responses across all age strata; for atopic dermatitis responses, the κ declined with increasing age, to 0.2613 for participants 65 or older.

Conclusions and Relevance  This cohort study found considerable agreement between responses over time when participants were asked about a history of psoriasis. When asked about a history of atopic dermatitis, responses over time were inconsistent. This inconsistency suggests that questionnaires on a history of atopic dermatitis will confer considerable risk of bias and misclassification.

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