Table 2.

Observed and expected concordances and Kappa coefficient for the comparisons between US, NCS and surgery

Comparison	Observed concordance	Expected concordance	Kappa coefficient	Standard error	z	p
US vs. surgery	84.4%	72.9%	0.423	0.083	5.08	< 0.001
NCS vs. surgery	92.2%	77.8%	0.648	0.090	7.22	< 0.001
US vs. NCS	76.5%	69.4%	0.232	0.091	2.54	0.006

NCS nerve conduction studies, US ultrasonography

There were 115 subjects in each comparison group