Abstract

Abstract Background Long Covid remains a relatively new phenomenon with emerging understanding. Estimated UK prevalence of Long Covid with three or more symptoms lasting for 12 weeks or more was 2.2% at the end of 2021. The population-based French SAPRIS-SERO cohort has novel information about the pattern of symptoms of Long Covid that has been obscured by controversy around the original paper. Methods Secondary analysis was used to describe and re-interpret the pattern of persistent symptoms by IgG seropositivity and self-reported Long Covid in the SAPRIS-SERO survey. Participants in the cross-sectional analysis were 26 823 individuals from the French population-based CONSTANCES cohort, included between 2012 and 2019, who took part in the nested SAPRIS and SAPRIS-SERO surveys. Between May and November 2020, the Euroimmun enzyme-linked immunosorbent assay was used to detect anti–SARS-CoV-2 antibodies. Surveyed online between December 2020 and January 2021, participants self-reported previous COVID-19 infection and physical symptoms during the previous four weeks that were new since March 2020, and had persisted for at least eight weeks. Results There was similarity of prevalence over the majority of symptoms in those self-reporting COVID-19 infection, regardless of blood test result. Persistent symptoms significantly associated with self-reported COVID-19 infection and common in both groups include respiratory tract symptoms and a group of symptoms that might be related to chronic fatigue, malaise or postural issues. Seropositivity for IgG antibodies did not predict symptoms independently of self-reported Long Covid, except for anosmia. Conclusions There may be three common sub-syndromes of Long Covid, one with persistent anosmia, another with other respiratory tract symptoms and a third, currently under researched, with symptoms relatable to chronic fatigue. Antibody tests are insufficient for case detection while Long Covid remains poorly understood. Key Messages IgG seropositivity is insufficient to identify potential cases of Long Covid Persistent anosmia is very strongly associated with IgG seropositivity and may define a subsyndrome of Long Covid Other potential subsyndromes are those with persistent respiratory symptoms and those with persistent symptoms relatable to fatigue, malaise or postural issues The Long Covid research effort should be rebalanced towards understanding the fatigue/tiredness subsyndrome.