Intra-assay Precision (Precision within an assay): 3 samples with low, middle and high level Complement Component 4d (C4d) were tested 20 times on one plate, respectively. Inter-assay Precision (Precision between assays): 3 samples with low, middle and high level Complement Component 4d (C4d) were tested on 3 different plates, 8 replicates in each plate. CV(%) = SD/meanX100. Intra-Assay: CV<10%. Inter-Assay: CV<12%