TABLE 1.

Differences in A_R values with and without immunoblocking procedure and in blocking efficiencies of mouse anti-EP Ab in indicated groups^a

Serum data group (no. of sera)	Blocking agent	Mean (SD) of difference	Significance at 95% levelb	% Blocking efficiency
False-positive	Anti-EPc	0.0712 (0.0328)	Yes**	25.07
sera (16)	NMSd	0.016 (0.0272)	No
Sera from healthy individuals (300)	Anti-EP	0.0079 (0.0209)	Yes**	0.0283
Sera from SARS patients (8)	NAe	NA (NA)	NA	0.0150

^aThe difference between the two blocking steps is defined by a paired Student's t test with a significance level of 95%. The A_R values of the 16 false positives in the standard rNP ELISA decreased significantly after the modified immunoblocking procedure. The blocking efficiency {Σ[(A_R-standard − A_R-modified)/A_R-standard]/n × 100%, in which A_R-standard and A_R-modified represent the A_R values with standard and modified blocking, respectively, and n represents the total number of samples} of the 16 false positives is obviously higher than those of the other two serum data groups.

^b**, P < 0.01.

^cAnti-EP, mouse anti-EP antiserum.

^dNMS, normal mouse serum.

^eNA, not applicable.