CD40LG and COVID-19: To this end, COVID-19 IgM/IgG test strips loaded with various predetermined, spiked amounts of IgG in serum (0, 0.5, 1, 5, 10, 100, 1000 ng/mL) were used to obtain the continuous reflectance spectra (from wavelengths 450 to 700 nm), where the data from three replicates were combined for the analysis.