Introduction: Post-COVID syndrome has been related with an inflammatory lingering state, as a result of an uncontrolled inflammatory cascade; even the likeness with an autoimmune disease has been questioned; that's why it is important to recognize inflammatory biomarkers to identify post-COVID patients and differentiate them from patients with an autoimmune disease, Post- COVID syndrome and healthy patients. Objective: To identify the inflammatory biomarkers that allows to sort the patients with previous SARS-COV-2 infection, by cytokine profiling. Methods: 145 patients were involved in this exploratory study all with previous SARS-COV-2 infection, the 41% with autoimmune disease patients, 50% patients with Post-COVID syndrome and 9% healthy patients. Clinical characteristics and a panel of 20 cytokines, multivariate methods were used to analyze the data. Results: The results of the classification tree show four possible cytokine profiles; 100% of the post-COVID syndrome patients has IL-9 levels >2.4pg/ml; Interleukin 9 (IL-9) levels were associated with the possibility of identifying the patients with post-COVID syndrome. The second cytokine profile is called autoimmunity that has lower IL-9 levels and IL-2 high levels (>1.3pg/ml). The third profile, which we call high probability of autoimmunity, has lower levels of IL-9 and IL-2 but higher levels of MCP-1 (4.3pg/ml); and the healthy patients have lower levels of all cytokines studied and this is the last profile of cytokines. Conclusion: The results highlight the importance of IL-9 as a key factor for the identification of Post-COVID syndrome, and also show that healthy patients have lower levels of inflammatory cytokines because they do not course with an inflammatory lingering state.
