Different definitions of atopic dermatitis: impact on prevalence estimates and associated risk factors

Abstract

SummaryBackgroundThere is no objective test that can unequivocally confirm the diagnosis of atopic dermatitis (AD), and no uniform clinical definition.ObjectivesTo investigate to what extent operational definitions of AD cause fluctuation in the prevalence estimates and the associated risk factors.MethodsWe first reviewed the operational definitions of AD used in the literature. We then tested the impact of the choice of the most common definitions of ‘cases’ and ‘controls’ on AD prevalence estimates and associated risk factors (including filaggrin mutations) among children aged 5 years in two population‐based birth cohorts: the Manchester Asthma and Allergy Study (MAAS) and Asthma in Ashford. Model performance was measured by the percentage of children within an area of clinical indecision (defined as having a posterior probability of AD between 25% and 60%).ResultsWe identified 59 different definitions of AD across 45 reviewed studies. Of those, we chose four common ‘case’ definitions and two definitions of ‘controls’. The prevalence estimates using different case definitions ranged between 22% and 33% in MAAS, and between 12% and 22% in Ashford. The area of clinical indecision ranged from 32% to 44% in MAAS and from 9% to 29% in Ashford. Depending on the case definition used, the associations with filaggrin mutations varied, with odds ratios (95% confidence intervals) ranging from 1·8 (1·1–2·9) to 2·2 (1·3–3·7) in MAAS and 1·7 (0·8–3·7) to 2·3 (1·2–4·5) in Ashford. Associations with filaggrin mutations also differed when using the same ‘case’ definition but different definitions of ‘controls’.ConclusionsUse of different definitions of AD results in substantial differences in prevalence estimates, the performance of prediction models and association with risk factors. What's already known about this topic? There is no objective test that can unequivocally confirm the diagnosis of atopic dermatitis (AD) and no uniform clinical definition.This results in different definitions utilized in AD studies, raising concerns on the generalizability of the results and comparability across different studies. What does this study add? This study has shown that different definitions of ‘cases’ and ‘controls’ have major impacts upon prevalence estimates and associations with risk factors, including genetics, in two population‐based birth cohorts.These findings suggest the importance of developing a consensus on AD definitions of both ‘controls’ and ‘cases’ to minimize biases in studies.

Interaction between filaggrin mutations and neonatal cat exposure in atopic dermatitis

“…Since AD is a chronic and relapsing disease, short episodes of other eczemas, for example, due to irritant or allergic contact dermatitis, may be misinterpreted as AD by parents and caregivers, in particular in the first years of life where flexural accentuation is not yet occurring. 4 Notably, the high prevalence of early AD in some cohorts, potentially due to unspecific diagnoses, could mask a true cat exposure-FLG mutation interaction. One may argue that AD measured at 7 years of age is expected to have a higher specificity due to flexural involvement.…”

“…is not yet occurring. 4 Notably, the high prevalence of early AD in some cohorts, potentially due to unspecific diagnoses, could mask a true cat exposure-FLG mutation interaction. One may argue that AD measured at 7 years of age is expected to have a higher specificity due to flexural involvement.…”

Epicutaneous sensitization in the development of food allergy: What is the evidence and how can this be prevented?

“…Atopic dermatitis (AD) affects approximately 20% to 30% of children. [1][2][3] Asthma affects 9%-18%, 4,5 and allergic rhinitis (AR) affects up to 40% of children. 6 Food allergy (FA) is an epidemic among children in Westernized countries [7][8][9] and significantly impairs quality of life.…”

Nomenclature and clinical phenotypes of atopic dermatitis

“…Differences in nomenclature create potential for confusion and for issues with the quality of epidemiologic data 24 given that AD and eczema are represented by different codes in the International Classification of Diseases, Tenth Revision (ICD-10), system. Besides the ICD-10 codes for AD (L20.x; Table 1 ), other ICD-10 codes can be used in diagnosis.…”