Operational definitions of asthma in recent epidemiological studies are inconsistent

Abstract

ObjectiveThe best combination of questions to define asthma in epidemiological asthma studies is not known. We summarized the operational definitions of asthma used in prevalence studies and empirically assess how asthma prevalence estimates vary depending on the definition used.MethodsWe searched the Thomson Reuters ISI Web of knowledge and included (1) cross-sectional studies (2) on asthma prevalence (3) conducted in the general population and (4) containing an explicit definition of asthma. The search was limited to the 100 most-cited papers or published since January 2010. For each paper, we recorded the asthma definition used and other variables. Then we applied the definitions to the data of the Portuguese National Asthma survey (INAsma) and of the 2005–2006 National Health and Nutrition Examination Survey (NHANES) computing asthma prevalence estimates for the different definitions.ResultsOf 1738 papers retrieved, 117 were included for analysis. Lifetime asthma, diagnosed asthma and current asthma were defined in 8, 12 and 29 different ways, respectively. By applying definitions of current asthma on INAsma and NHANES data, the prevalence ranged between 5.3%-24.4% and 1.1%-17.2%, respectively.ConclusionsThere is considerable heterogeneity in the definitions of asthma used in epidemiological studies leading to highly variable estimates of asthma prevalence. Studies to inform a standardized operational definition are needed. Meanwhile, we propose a set of questions to be reported when defining asthma in epidemiological studies.

Allergic disease and Staphylococcus aureus carriage in adolescents in the Arctic region of Norway

“…All rights reserved. 23 of 46 (50%) samples from eczematous skin of whom 21 (91.3%) also had nasal carriage. Figure 2b shows that participants with eczematous S. aureus skin carriage had higher POEM score (mean 14.1, SD 6.9) compared to participants without S. aureus skin carriage (mean 8.5, SD 4.8) (p=0.003).…”

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“…In fact, the best combination of questions to define asthma in epidemiological studies is not known. A recent review summarized the operational asthma definitions used in prevalence studies and evaluated how asthma prevalence estimates vary depending on the definition used [6]. In the literature, lifetime asthma, diagnosed asthma and current asthma were defined in 8, 12 and 29 different ways, respectively.…”

“…By applying definitions of current asthma to data from the 2010 Portuguese National Asthma Survey (INAsma) [7] and the 2005-2006 National Health and Nutrition Examination Survey (NHANES) [8], the prevalence ranged between 5.3 to 24.4% and 1.1 to 17.2%, respectively. The authors concluded that epidemiological asthma definitions can lead to highly variable estimates of asthma prevalence and a standardized operational definition is needed [6]. …”

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“…However, there is no uniform approach in identifying survey respondents with asthma, and the use of the differing classification criteria may have a substantial effect on prevalence estimates [18]. Furthermore, although different classifications may result in similar prevalence estimates, they may not be capturing the same population [19].…”

“…Furthermore, although different classifications may result in similar prevalence estimates, they may not be capturing the same population [19]. This may lead to study results that are biased and ultimately not comparable with results from other studies [18,20]. …”