CD40LG and congestive heart failure: Assay performance was evaluated in comparison with in-house gold standard testing by IgM/IgG indirect immunofluorescence (IIF) and commercially available IgM/IgG ELISA tests (VectoCrimean-CHF-IgM/IgG, Vector-Best, Russia) using a serum panel comprising paired samples from 15 Kosovar patients with an RT-PCR-confirmed acute CCHFV-infection and 12 follow-up samples from the same group of patients taken approximately one year after they had overcome the disease.