Development of the 8-Item Phlegm Pattern Questionnaire (PPQ-8) Using Rasch Analysis

Table 7

Receiver operating characteristic (ROC) curve analyses of the EITC and the Rasch models.

The 8-item questionnaire by EITC	The 8-item questionnaire by Rasch analysis
Points	Sensitivity	Specificity	Youden index	Euclidean distance	Points	Sensitivity	Specificity	Youden index	Euclidean distance
18.5	0.886	0.471	0.357	0.541	15.5	0.909	0.353	0.262	0.653
19.5	0.864	0.471	0.335	0.546	16.5	0.909	0.412	0.321	0.595
20.5	0.818	0.471	0.289	0.559	17.5	0.864	0.412	0.275	0.604
21.9	0.773	0.588	0.361	0.470	18.5	0.841	0.471	0.311	0.553
22.5	0.727	0.706	0.433	0.401	19.5	0.795	0.529	0.325	0.513
23.5	0.705	0.706	0.411	0.416	20.5	0.727	0.588	0.316	0.494
24.5	0.705	0.765	0.470	0.377	21.5	0.727	0.647	0.374	0.446
25.5	0.659	0.824	0.483	0.384	22.5	0.705	0.765	0.469	0.378
26.5	0.636	0.824	0.460	0.404	23.5	0.636	0.765	0.401	0.433
27.5	0.614	0.882	0.496	0.404	24.5	0.500	0.824	0.324	0.530
28.4	0.591	0.882	0.473	0.426	25.5	0.432	0.824	0.255	0.595
28.9	0.568	0.882	0.450	0.448	26.5	0.409	0.882	0.291	0.603
29.5	0.409	0.882	0.291	0.603	27.5	0.341	0.882	0.223	0.670
31.0	0.341	0.882	0.223	0.669	28.5	0.273	0.882	0.155	0.737
32.5	0.318	0.882	0.200	0.692	29.5	0.205	0.882	0.087	0.804

The values in bold indicate the maximum Youden index and minimum Euclidean distance obtained using ROC curve analyses.