Enzyme-linked immunosorbent assay (ELISA) is the most popular methodology for absolute quantification of particular proteins in liquid samples. Especially for CCN family members that are associated with human diseases, utility of ELISA for those proteins in clinics as well as research laboratories is emphasized. However, in order to obtain accurate and stable results in ELISA, particular care should be taken in controlling the quality and quantity of standard CCN family proteins, which bind to various materials and can be unstable in a purified form. Recently, diagnostic value of the CCN family protein fragments in body fluids has been indicated in several diseases. Therefore, module-specific detection system for the CCN family members is desired as a promising tool in clinics. It should be also noted that modular fragments of CCN family members can be more stable than the full-length in purified forms, whose quality may be easier to control than that of the full-length ones.