In the COVID-19-positive group, hemoglobin, hematocrit, white blood cells, lymphocytes, monocytes, basophils, C3 Complement, total cholesterol, LDL cholesterol, prothrombin time (PT), thyroid stimulating hormone (TSH), free T4 and estimated glomerular filtration rate (eGFR) eGFR were lower. Here, C3 is linked to COVID-19.