Table 6.

ROC curve analysis for LCQ score thresholds predictive of PGIC of 1 to 3 at week 4.

LCQ score-change threshold	Sensitivity	Specificity	Positive predictive value	Negative predictive value	Youden index
Total score
⩾1.0	0.83	0.70	0.87	0.64	0.53
⩾1.3	0.81	0.76	0.89	0.62	0.56
⩾1.5	0.78	0.81	0.91	0.61	0.60
⩾1.7	0.76	0.86	0.93	0.60	0.61
⩾2.0	0.72	0.89	0.94	0.57	0.61
⩾2.3	0.68	0.91	0.95	0.55	0.60
⩾2.7	0.64	0.94	0.96	0.53	0.59
⩾3.0	0.56	0.94	0.96	0.47	0.50
Physical
⩾0.8	0.49	0.94	0.95	0.44	0.43
⩾0.9	0.44	0.94	0.95	0.42	0.39
Psychological
⩾0.9	0.62	0.89	0.93	0.50	0.51
⩾1.0	0.62	0.89	0.93	0.50	0.51
Social
⩾0.8	0.65	0.86	0.92	0.51	0.51
⩾0.9	0.65	0.86	0.92	0.51	0.51
⩾1.0	0.65	0.86	0.92	0.51	0.51

LCQ, Leicester Cough Questionnaire; PGIC, patient global impression of change; ROC, receiver operating characteristic.