To identify the variables most strongly associated with COVID-19 severity, we finally compared the results of the five different approaches and observed that the relative neutrophil and lymphocyte count, together with the inflammatory markers MCP3 [50], IL6 [16], TRANCE [63], and MCP1 [24]; the neurology-associated markers CD200R1 [54], α2-MRAP [54], and MATN3 [54]; and the cardiometabolic markers KIT and LTBP2 [39] emerged in at least four of the analyses conducted. This evidence concerns the gene CCL2 and COVID-19.