To the Editor: We congratulate Hill and colleagues1 for their timely research on the performance of symptom assessment smartphone applications (apps) in Australia. The apps in the study were selected using structured criteria2 to identify those featuring most prominently in internet search engines and app stores. However, we note that this strategy is biased against an important class of symptom checkers. Because the app store search included “medical diagnosis” and “health symptom diagnosis”, the authors’ approach was less likely to identify many symptom checkers regulated in Europe under the CE (Conformité Européene) Marking system. Specifically, these apps must not describe themselves as “diagnostic tools”, as diagnosis is a function carried out by a doctor. We believe this to be the reason why the CE‐marked Ada health assessment app was not identified or selected by the authors.1 This represents a missed opportunity for analysis, as Ada has been freely available in Australia since 2016,3 and was downloaded at least 200 times more frequently in Australia between November 2018 and January 2019 than either Symptomate or Symcat, which were included in the study (App Annie [www.appannie.com] download data; viewed June 2020). Other studies have found that the Ada app performs well when compared with the other apps assessed, as recently published.4
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