CD40LG and cytomegalovirus infection: Based on the results of IgG avidity in IgM/IgG positive samples, recent primary CMV infections were confirmed by low and borderline AI in 25 (0.8%; 95% CI: 0.6–1.3) patients, while in others (IgG antibodies of high avidity), detectable IgM antibodies indicated recurrent CMV infection.