Toward a Universal Definition of Post–COVID-19 Condition—How Do We Proceed?
Daniel Pan, Manish Pareek
Abstract
The phrase "post-COVID-19 condition" (PCC) (sometimes called long COVID) refers to a large collection of symptoms and signs experienced by patients with COVID-19 following initial infection with SARS-CoV-2.With more than 651 million documented COVID-19 cases worldwide and a conservative estimated prevalence of 10% infected, 65 million individuals around the world are likely to have PCC. 1 Chaichana and colleagues 2 investigated how PCC was defined within the existing published scientific literature.The authors investigated whether included studies presented definitions of PCC that matched those used in guidance from the National Institute for Health and Care Excellence (NICE), World Health Organisation (WHO) and the Centers for Disease Control and Prevention (CDC).The authors found that only approximately a third of 295 studies used official PCC definitions.Instead, most studies used their own definitions for PCC, while 64 studies did not define PCC at all.How do these findings affect the PCC landscape?First, the lack of a consistent definition for PCC between organizations and studies makes assimilating and comparing findings from current studies difficult.There is also multiplicity of titles for what appears to be the same clinical problem-for example, long COVID, post-COVID symptoms, post-COVID syndrome, post-COVID condition, and post-acute COVID, among others.By using different definitions and titles, different studies will have focused on different people, symptoms, and time intervals and hence, any estimated prevalence or incidence of PCC will vary widely between studies, even if conducted in the same time period in the same population.Second, in the generation of their definitions, many studies will require the reporting of an initial infection episode; either self-reported or through molecular testing.However, initial lack of awareness of the range of symptoms associated with acute COVID-19 by the general population will mean that many people without access to testing may have not associated their symptoms with acute infection and therefore did not associate any enduring symptoms with PCC.Therefore, it is likely that current estimates are underestimating the true burden of those with PCC.