Comparison of the COPD Population Screener and International Primary Care Airway Group questionnaires in a general Japanese population: the Hisayama study

Figures & data

Table 1 Baseline characteristics

Characteristics	No AOa		AOa	Kruskal–Wallis test (P-value)
	Pre-BD FEV1≥70%	Pre-BD FEV1 <70%
Subjects, n	2,076	110	150
Age (years), mean (SD)	60.3 (10.5)	65.0 (9.4)	66.5 (8.9)	<0.0001
Male (%)	41.7	45.5	68.7
BMI (kg/m^2), mean (SD)	23.3 (3.4)	22.8 (2.9)	22.2 (3.0)	<0.001
Pack-year				<0.0001
Mean (SD)	11.6 (19.7)	15.6 (21.5)	31.0 (30.7)
Median (IQR)	0 (0–19.5)	0 (0–30.8)	26.5 (0–47.5)
Smoking status (%)
Never	59.3	52.7	28.0
Former	25.4	24.5	35.3
Current	15.3	22.7	36.7
COPD-PS score				<0.001
Mean (SD)	2.4 (1.4)	2.9 (1.4)	3.9 (1.7)
Median (IQR)	2 (2–4)	2 (2–4)	4 (2–5)
IPAG questionnaire score, mean (SD)	16.7 (4.9)	18.8 (4.0)	22.0 (5.0)	<0.0001
%FVC, mean (SD)	100.7 (13.0)	101.4 (13.6)	96.4 (16.6)	<0.01
Pre-BD FEV1% predicted, mean (SD)	95.4 (13.2)	84.8 (12.2)	74.6 (16.7)	<0.0001
Post-BD FEV1% predicted, mean (SD)	NA	91.2 (13.0)	77.9 (16.7)	<0.0001
Pre-BD FEV1%, mean (SD)	77.7 (4.6)	67.6 (2.6)	62.2 (6.4)	<0.0001
Post-BD FEV1%, mean (SD)	NA	73.6 (3.6)	63.2 (6.8)	<0.0001
Reversibility (%)	NA	29.1	18.0
COPD stage (%)
Mild	NA	NA	46.0
Moderate	NA	NA	48.0
Severe	NA	NA	5.3
Very severe	NA	NA	0.7

Notes:

a No AO, post-BD FEV₁/FVC ≥0.7; AO, post-BD FEV₁/FVC <0.7.

Abbreviations: AO, airflow obstruction; BD, bronchodilator; FEV₁, forced expiratory volume in 1 second; BMI, body mass index; IQR, interquartile range; COPD-PS, COPD Population Screener; IPAG, International Primary Care Airway Group; FVC, Forced Vital Capacity; NA, not applicable; SD, standard deviation.

Table 2 Strength of the association between informant and performance measures

Variable	COPD-PS	IPAG questionnaire
IPAG questionnaire	0.622*	–
%FVC	−0.117*	−0.033**
FEV1%	−0.301*	−0.356*

Notes:

* P-values <0.001 for Pearson’s correlation coefficients.

** P-values <0.01 for Pearson’s correlation coefficients.

Abbreviations: COPD-PS, COPD Population Screener; IPAG, International Primary Care Airway Group; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second.

Table 3 Cutpoint evaluation of COPD-PS and IPAG questionnaires to discriminate between AO and no AO states

Screening questionnaire	Cutpoint	OR	Sensitivity (%)	Specificity (%)	Positive predictive value (%)	Negative predictive value (%)	Percent correctly classified	AUC
COPD-PS	4	5.52	66.7	73.4	14.7	97.0	73.0	0.70
IPAG	16	5.20	88.7	39.9	9.2	98.1	43.1	0.64
	17	5.28	86.0	46.2	9.9	98.0	48.8	0.66
	18	5.51	84.0	51.2	10.6	97.9	53.3	0.68
	19	5.48	78.7	59.8	11.8	97.6	61.0	0.69
	20	6.56	71.3	72.5	15.1	97.4	72.4	0.72
	21	6.62	70.0	73.9	15.6	97.3	73.7	0.72

Abbreviations: COPD-PS, COPD Population Screener; IPAG, International Primary Care Airway Group; AO, airflow obstruction; OR, odds ratio; AUC, area under the receiver operating characteristic curve.

Figure 1 Receiver operating characteristic curve of the COPD-PS and the IPAG questionnaires to discriminate between the subjects with and without AO.

Abbreviations: COPD-PS, COPD Population Screener; IPAG, International Primary Care Airway Group; AO, airflow obstruction.

Table 4 Discriminative ability of the COPD-PS and IPAG questionnaires

Variable	AO vs no AO
	COPD-PS	IPAG questionnaire
AUC	0.747 (0.707–0.788)	0.775 (0.735–0.816)
Sensitivity	66.7 (59.1–74.2)	71.3 (64.1–78.6)
Specificity	73.4 (71.6–75.3)	72.5 (70.6–74.4)
PPV	14.7 (9.0–20.3)	15.1 (9.4–20.8)
NPV	97.0 (96.2–97.8)	97.4 (96.6–98.1)
LR+	2.51 (2.49–2.53)	2.59 (2.57–2.61)
LR−	0.45 (0.44–0.47)	0.40 (0.38–0.41)

Note: Values are represented as AUC (95% CI).

Abbreviations: COPD-PS, COPD Population Screener; IPAG, International Primary Care Airway Group; AO, airflow obstruction; AUC, area under the receiver operating characteristic curve; PPV, positive predictive value; NPV, negative predictive value; LR, likelihood ratio.

Table 5 Reclassification among subjects with and without AO

Model with IPAG questionnaire	Model with COPD-PS
	Q1	Q2	Q3	Q4	Total
No AO
Q1	302	135	46	21	504
Q2	165	251	110	89	615
Q3	11	249	89	148	497
Q4	3	197	47	323	570
Total	481	832	292	581	2,186
AO
Q1	4	5	0	0	9
Q2	1	7	3	4	15
Q3	0	9	3	9	21
Q4	0	13	5	87	105
Total	5	34	11	100	150

Notes: NRI =−0.1073; IDI =−0.0135. Frequency across the four strata risks. Model with COPD-PS vs model with IPAG questionnaire.

Abbreviations: AO, airflow obstruction; COPD-PS, COPD Population Screener; IPAG, International Primary Care Airway Group; NRI, net reclassification improvement; IDI, integrated discrimination improvement; Q1, first quartile; Q2, second quartile; Q3, third quartile; Q4, fourth quartile.