Complement-mediated renal diseases after kidney transplantation - current diagnostic and therapeutic options in de novo and recurrent diseases

Table 6 Monitoring eculizumab therapy

CH50 (total complement activity)	AH50 (alternative pathway hemolytic activity)	Eculizumab trough	Alternative assays
Measures the combined activity of all of the complement pathways	Measures combined activity of alternative and terminal complement pathways	May be a free or bound level	The following assays are under investigation
Tests the functional capability of serum complement components to lyse 50 % of sheep erythrocytes in a reaction mixture	Tests functional capability of alternate or terminal pathway complement components to lyse 50% of rabbit erythrocytes in a Mg2+-EGTA buffer	ELISA: using C5-coated plates, patient sera, and an anti-human IgG detection system	Free C5
Low in congenital complement deficiency (C1-8) or during complement blockade	Will be low in congenital C3, FI, FB, properdin, FH, and FD deficiencies or during terminal complement blockade	Not affected by complement deficiencies	In vitro human microvascular endothelial cell test
Normal range: Assay dependent	Normal range is assay-dependent.	Recommended trough level during complement blockade: 50-100 μg/mL	SC5b-9 (also referred to as sMAC and TCC) remain detectable in aHUS remission, so not recommended as a monitoring tool
Recommended goal during therapeutic complement blockade: < 10% of normal	Recommended goal during complement blockade: < 10% of normal

Adapted from Goodship et al[12]. aHUS: Atypical hemolytic uremic syndrome; C3: Complement component 3; C5: Complement component 5; EGTA: Ethyleneglycol tetraacetic acid; ELISA: Enzyme-linked immunosorbent assay; FB: Complement factor B; FD: Complement factor D; FH: Complement factor H; FI: Complement factor I; sC5b-9: Soluble C5b-9; sMAC: Soluble membrane attack complex; TCC: Terminal complement complex.