TABLE 5.

Optimal competition time of the mixture containing sera and PRRSV-N-Nb1-HRP fusion proteins incubated with the antigen and colorimetric reaction using a checkerboard assay with cELISA^a

Times of color reaction (min)	Sera type	Incubation time (min) of antigens, sera, and PRRSV-Nb1-HRP fusions
		20	30	40
10	Positive	0.057	0.165	0.173
	Negative	0.103	1.031	1.077
	P/N	0.553	0.160	0.161
15	Positive	0.057	0.168	0.183
	Negative	0.103	1.066	1.103
	P/N	0.553	0.158	0.166
20	Positive	0.058	0.172	0.202
	Negative	0.117	1.068	1.088
	P/N	0.496	0.161	0.186

^a The best competition time and colorimetric reaction time was also selected when the OD_450nm values of positive to negative (P/N) sera was smallest.