By doing stepwise multiple linear regression analysis on age, BMI, D-dimer, CRP, Ct value, and SpO2, we found that model 1 (Ct value alone), model 2 (Ct value and age), model 3 (Ct value, age, and BMI), and model 4 (Ct value, age, BMI, and D-dimer) were strongly associated to SpO2 dropping in COVID-19 patients. The gene discussed is CRP; the disease is COVID-19.