Investigating sensitivity, specificity, and area under the curve of the Clinical COPD Questionnaire, COPD Assessment Test, and Modified Medical Research Council scale according to GOLD using St George’s Respiratory Questionnaire cutoff 25 (and 20) as reference

Figures & data

Table 1 Patient characteristics

	Data set A (n=238)	Data set B (n=101)	P-value
Age (years)	57.18±7.10	66.07±8.80	<0.001
Sex			<0.001
Female	87 (36.6)	9 (8.9)
Male	151 (63.4)	92 (91.1)
BMI (kg/m^2)	26.96±6.49	28.33±5.34	0.061
Smoking behavior
Smoking (pack-years)	40.22±24.64	63.85±35.30	<0.001
Spirometry
FEV1, L	1.55±0.58	1.53±0.59	0.807
FEV1 % predicted	51.16±15.67	56.21±18.75	0.015
Health status
mMRC scale	2.53±1.22	0.85±0.94	<0.001
SGRQ total	50.13±17.99	35.24±17.41	<0.001
CCQ total	2.85±1.19	1.52±0.94	<0.001
CAT total	20.18±7.59	12.65±7.45	<0.001

Note: Data expressed as means ± standard deviation or frequency (%).

Abbreviations: BMI, body mass index; CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; FEV₁, forced expiratory volume in 1 second; mMRC, modified Medical Research Council; SGRQ, St George’s Respiratory Questionnaire.

Table 2 Differences between two AUCs for the SGRQ cutoff points 20 and 25

	Questionnaires	AUCs	P-value
SGRQ cut point 20
Study A	CCQ, CAT	0.986, 0.943	<0.01*
	CCQ, mMRC scale	0.986, 0.935	0.10
	CAT, mMRC scale	0.943, 0.935	0.80
Study B	CCQ, CAT	0.894, 0.800	0.06
	CCQ, mMRC scale	0.894, 0.811	0.04*
	CAT, mMRC scale	0.800, 0.811	0.85
SGRQ cut point 25
Study A	CCQ, CAT	0.964, 0.885	<0.001*
	CCQ, mMRC scale	0.964, 0.912	0.07
	CAT, mMRC scale	0.885, 0.912	0.46
Study B	CCQ, CAT	0.899, 0.822	0.04*
	CCQ, mMRC scale	0.899, 0.809	0.03*
	CAT, mMRC scale	0.822, 0.809	0.80

* Note: P<0.05.

Abbreviations: AUCs, areas under the curve; CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; mMRC, modified Medical Research Council; SGRQ, St George’s Respiratory Questionnaire.

Table 3 Results from the ROC-curve analysis for the SGRQ cut points 20 and 25

	Cut point SGRQ ≥25			Cut point SGRQ ≥20
	Sensitivity 95% CI	Specificity 95% CI	AUC 95% CI	Sensitivity 95% CI	Specificity 95% CI	AUC 95% CI
CCQ
Study A	0.99	0.43	0.96	0.99	0.73	0.99
	0.95–1	0.34–0.53	0.94–0.99	0.95–1	0.64–0.81	0.97–1
Study B	0.87	0.77	0.9	0.8	0.89	0.89
	0.79–0.92	0.68–0.84	0.84–0.96	0.71–0.87	0.81–0.94	0.83–0.96
CAT
Study A	0.92	0.48	0.89	0.91	0.73	0.94
	0.85–0.96	0.38–0.58	0.83–0.94	0.84–0.95	0.64–0.81	0.91–0.98
Study B	0.76	0.73	0.82	0.69	0.78	0.80
	0.67–0.83	0.64–0.81	0.73–0.92	0.59–0.77	0.69–0.85	0.68–0.92
mMRC scale
Study A	0.68	0.91	0.91	0.66	0.95	0.94
	0.58–0.76	0.84–0.95	0.86–0.97	0.56–0.75	0.89–0.98	0.87–1
Study B	0.21	1	0.81	0.18	1	0.81
	0.14–0.3	0.96–1	0.73–0.89	0.12–0.27	0.96–1	0.72–0.9

Notes: ROC results for mMRC 1.5 and 2.5 provided. Since median =2, the average of both values was calculated.

Abbreviations: AUC, area under the curve; CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; CI, confidence interval; mMRC, modified Medical Research Council; ROC, receiver-operating characteristic; SGRQ, St George’s Respiratory Questionnaire.

Figure 1 ROC curves (study A) for SGRQ cut point ≥25.

Abbreviations: CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; mMRC, modified Medical Research Council; ROC, receiver-operating characteristic; SGRQ, St George’s Respiratory Questionnaire.

Figure 2 ROC curves (study B) for SGRQ cut point ≥25.

Abbreviations: CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; mMRC, modified Medical Research Council; ROC, receiver-operating characteristic; SGRQ, St George’s Respiratory Questionnaire.

Figure 3 ROC curves (study A) for SGRQ cut point ≥20.

Abbreviations: CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; mMRC, modified Medical Research Council; ROC, receiver-operating characteristic; SGRQ, St George’s Respiratory Questionnaire.

Figure 4 ROC curves (study B) for SGRQ cut point ≥20.

Abbreviations: CAT, COPD Assessment Test; CCQ, Clinical COPD Questionnaire; mMRC, modified Medical Research Council; ROC, receiver-operating characteristic; SGRQ, St George’s Respiratory Questionnaire.