TABLE 2.

MAb methodologies used in this study^a

Method	IFX	ADM	RTX	CERT	VEDO	ECU
Non-MS-based methods
Cell-based reporter gene assay	X (27)	X (27)
ELISA	X	X		X	X	X
Electrochemiluminescence immunoassay	X	X	X
Homogeneous mobility shift assay	X (25)	X (64)			X
MS-based methods
Tryptic digest by LC-MS/MS	X (59)	Lack of unique tryptic peptide sequences; peptides found in a few healthy subjects not taking drug at clinically relevant concn	Not studied	Not studied	Method developed and quantitation of VEDO possible with unique light chain tryptic peptides (data not shown)	Quantitation of ECU possible with unique light-chain tryptic peptides (data not shown)
Intact light chain by LC-MS	In initial feasibility studies, did not meet required LOQ with Melon Gel as preanalytical enrichment method	In initial feasibility studies, did not meet required LOQ with Melon Gel as preanalytical enrichment method	RTX light chain characterized and measured in a series of samples; however, clinical utility remains to be shown (61)	Not studied	VEDO light chain characterized with Melon Gel as preanalytical enrichment method (data not shown)	Quantitation achieved by IgG4 preanalytical sample enrichment and intact ECU light-chain accurate mass (63)

^aX, commercially available in CLIA-certified laboratories. Reference numbers are in parentheses. Comments are from the authors' experience with MS methods.