Table 2.

Characteristics of various types of ELISA

	Direct ELISA	Competitive ELISA	Indirect ELISA	Indirect competitive ELISA	Sandwich ELISA
Advantage	Simple because only one antibody is used		Higher sensitivity and versatility than direct methods owing to usage of PAb that recognizes different epitopes of primary antibody		High specificity as two antibodies possessing different epitopes are used
Disadvantage	Labeling antibody is necessary for each ELISA, which may result in inactivation of antibody		Nonspecific signal is induced through cross-reactivity of secondary antibody		To prepare two different antibodies is labor-intensive and expensive
Target	Macromolecules	Macromolecules (Hapten)	Macromolecules	Macromolecules (Hapten)	Generally macromolecules
Signal (as target antigen increase)	Increase	Decrease	Increase	Decrease	Increase