Inflammatory profiles are associated with long COVID up to 6 months after illness onset: A prospective cohort study of patients with mild to critical COVID-19 7 211 vaccination. All serum samples were processed within 24 hours and stored at -80⁰C. In the present study, we defined three time-frames of sample collection for longitudinal analyses: 0-4, 9-12 and 21-24 weeks after illness onset. Post-vaccination samples were defined as those collected within 28 days after administration of a COVID-19 vaccine. Definitions Illness onset was defined as the earliest day of COVID-19 symptoms were experienced for symptomatic patients, or date of SARS-CoV-2 diagnosis for asymptomatic patients. PASC was defined as reporting at least one COVID-19 symptom that, from illness onset, occurred within one month and continued beyond 12 weeks[3]; symptoms arising after one month from illness onset were not attributed to PASC. COVID-19 clinical severity was categorised according to WHO criteria [14]. BMI was coded in kg/m2 as: <25, underweight or normal weight; 25-29, overweight; ≥30, obese. Diffusion capacity (DLCO) at 6 months after illness onset was defined as impaired according to American Thoracic Society (ATS) European Respiratory Society guidelines[18], as described previously described[17]. Inflammation marker assays C-reactive protein (CRP), CD14, CD163, tumor necrosis factor (TNF)-α, interferonγ-inducible protein 10 (IP-10)/CXCL10, monocyte chemoattractant protein (MCP)1/ CCL2, interleukin (IL)1β IL2, IL6, IL10, IL13 and IL17A, concentrations were analyzed in serum by human magnetic luminex screening assay (LXSAHM-02 and LXSAHM-10; R&D Systems). Assays were performed according to the manufacturer’s instructions. Using immunofluorescence, titers of total antinuclear antibodies (ANA) as indicators of possible auto-immunity were determined for samples collected ≤4 weeks after illness onset. Statistical analysis Socio-demographic, clinical and study characteristics were compared between included participants with and without PASC at 12 weeks after illness onset. To assess selection bias, we compared features of included and excluded participants. We used the Fisher’s exact test to evaluate the association between PASC and impaired diffusion capacity at 6 months after illness onset. We presented box-and-whisker plots of median (IQR) log-concentrations of cytokines at 9-12 and 21-24 weeks after illness onset, comparing in univariable analyses: i) with reference samples from uninfected, healthy individuals and ii) between study
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