All these 20 laboratories used IgM assays for detecting acute infection (IgM and IgG positive) and there were a total of 27 submissions of IgM results, while 19 laboratories tested the panel samples also for previous or recent infection (positive IgG and negative IgM), adding up to a total of 27 submissions of IgG results from these 19 laboratories (Figure 1B). Here, CD40LG is linked to infection.