Serum and plasma levels of Ba, but not those of soluble C5b-9, might be affected by renal function in chronic kidney disease patients

Background During the last few decades, pathogenic mechanisms associated with uncontrolled activation of the complement (C) system and development of anti-C agents have been closely investigated in the field of nephrology. The usefulness of some C products such as C5a and sC5b-9 for diagnostic and prognostic purposes remains controversial. On the other hand, decreased renal function is being observed in many patients with or without nephritis as a background factor in progressively aging societies. We therefore investigated whether renal function influenced the evaluation of various complement components and activation products. Methods To investigate the influence of renal function on evaluations of C3, C4, CH50, Ba, C5a and sC5b-9, 40 patients were retrospectively chosen from among 844 patients without active glomerulonephritis from 2009 to 2016. We measured plasma and serum levels of C3, C4, CH50, Ba, C5a and sC5b-9 using enzyme-linked immunosorbent assays and compared the findings with inulin clearance (Cin) as a marker of preserved renal function. Results Both plasma and serum levels of Ba correlated significantly with Cin, but other values did not. Compared with patients with Cin ≥ 60 or ≥ 30 mL/min/1.73 m 2 , plasma and serum levels of Ba were increased in patients with Cin decreased to < 60 or < 30 mL/min/1.73 m 2 , but levels of C5a and sC5b-9 were not. Conclusion The influence of renal function might need to be considered when evaluating Ba, but not C5a and sC5b-9, in plasma and serum samples from chronic kidney disease patients.