Development and validation of a telephone classification interview for common chronic headache disorders

Table 2 Summary of proportion of concordance, simple kappa coefficient, κ, (95% confidence interval, CI), maximum attainable kappa, κ_max, and prevalence-adjusted bias-adjusted kappa, PABAK (95% CI)

Comparison	Proportion of concordance	κ	95% CI	κ_max	PABAK	95% CI
Chronic migraine vs. others^a	0.76	0.31	(0.09 to 0.52)	0.79	0.51	(0.35 to 0.68)
Chronic migraine vs. chronic TTH^b	0.96	0.38	(−0.18 to 0.94)	0.79	0.92	(0.83 to 1.00)
With MOH vs. without MOH^c	0.76	0.40	(0.17 to 0.63)	0.93	0.51	(0.32 to 0.71)

^aChronic migraine = definite chronic migraine or probable chronic migraine; Others = chronic tension type, other chronic headaches or non-chronic headaches
^bChronic migraine = definite chronic migraine or probable chronic migraine; chronic TTH = chronic tension type headache
^cMOH, medication overuse headache

ISSN: 1129-2377