A total of 34 serum samples collected from COVID-19 patients admitted to Wuhan Huoshenshan Hospital were tested with a SARS-CoV-2-specific IgM Ab detection kit based on the capture method, produced by manufacturer C. Before testing, serum samples were heat-inactivated at 56°C for 30 min or 60°C for 30 min in a water bath. The gene discussed is CD40LG; the disease is COVID-19.