Table 1.

Diagnostic agreement by Cohen’s kappa score for the reference diphtheria toxin neutralization test (TNT) vs. the multiplex bead assay (MBA)

Antibody level (IU/ml)		TNT			% agreement (95% CI)	Kappa score (95% CI)
		≥0.1 (n=659)	0.016 to <0.1 (n=312)	<0.016 (n=329)
MBA	≥0.1	516	5	2	81% (79%–83%)	0.71 (0.68–0.74)
	0.010 to <0.1	139	264	54
	<0.01	4	43	273
	≥0.1	516	5	2	80% (78%–82%)	0.70 (0.66–0.73)
	0.015 to <0.1	139	224	23
	<0.015	4	83	304