Table 1.

Sensitivity, specificity, and predictive values of retrospective headache reports (last one year) vs. three-week prospective diary recordings

		Diary
		Headache	No headache	Total
Interview	Headache	304	42	346	PPVa:304/346 = 88 %
	No headache	23	24	47	NPVb:24/47 = 51 %
	Total	327	66	393
		Sensitivity: 304/327 = 93 %	Specificity: 24/66 = 36 %

Kappa: 0.33 (95 % CI: 0.20–0.45). McNemar–Bowker test of cell proportion symmetry: p = 0.019

^aPositive predictive value

^bNegative predictive value

Only participants who filled in the diary for ≥1 day are included in the table