Diagnostic Accuracy of a Two-Stage Sequential Screening Strategy Implemented by Community Health Workers (CHWs) to Identify Individuals with COPD in Rural India

Figures & data

Figure 1 Participant flow diagram.

Abbreviations: LFQ, Lung Function Questionnaire; BD, bronchodilation.

Table 1 Comparison of Demographic Characteristics of the Study Participants (N=3256)

Variables	Participants without Spirometry (n=2988)	Participants Randomly Selected for Spirometry (n=268)	p-value
Mean age in years (±SD)	56.5 (±12.2)	56.7 (±10.4)	0.83
Men, n (%)	1233 (41.3)	123 (45.9)	0.14
Able to read and understand LFQ*, n (%)	1323 (44.3)	199 (48.1)	0.22
How often do you cough up mucus?, n (%)
Never	1980 (66.3%)	163 (60.8%)	0.15
Rarely	327 (10.9%)	35 (13.1%)
Sometimes	369 (12.4%)	33 (12.3%)
Often	149 (5.0%)	14 (5.3%)
Very often	163 (5.5%)	23 (8.7%)
How often does your chest sound noisy (wheezy, whistling, rattling) when you breathe?, n (%)
Never	2301 (77.0%)	202 (75.4%)	0.48
Rarely	247 (8.3%)	20 (7.5%)
Sometimes	220 (7.4%)	28 (10.5%)
Often	133 (4.5%)	11 (4.1%)
Very often	87 (2.9%)	7 (2.6%)
How often do you experience shortness of breath during physical activity (walking up a flight of stairs or walking up an incline without stopping to rest)?, n (%)
Never	1544 (51.7%)	123 (45.9%)	0.16
Rarely	268 (9.0%)	21 (7.8%)
Sometimes	444 (14.9%)	51 (19.0%)
Often	395 (13.2%)	35 (13.1%)
Very often	337 (11.3%)	38 (14.2%)
How many years have you smoked?, n (%)
Never smoked	1697 (56.8%)	143 (53.4%)	0.09
≤10 years	237 (8.0%)	14 (5.2%)
11–20 years	254 (8.5%)	25 (9.3%)
21–30 years	174 (5.8%)	13 (4.9%)
>30 years	626 (21.0%)	73 (27.2%)
Mean LFQ score (±SD)	19.1 (±4.0)	18.4 (±3.9)	0.01

Notes: *The LFQ items/questions are reproduced from Hanania NA, Mannino DM, Yawn BP, et al. Predicting risk of airflow obstruction in primary care: Validation of the lung function questionnaire (LFQ). Respiratory Medicine. 2010;104(8):1160–1170. Copyright 2010 Elsevier Ltd. All rights reserved.¹⁶

Abbreviation: LFQ, Lung Function Questionnaire.

Table 2 Comparison of Lung Function Parameters (FEV₁ and FEV₆) of Participants Obtained from the Three Best Forced Expiratory Manoeuvres on the Pocket Spirometer

Parameters N = 268	FEV1 Blow 1	FEV1 Blow 2	FEV1 Blow 3	FEV6 Blow 1	FEV6 Blow 2	FEV6 Blow 3
Mean	1.57	1.63	1.65	2.14	2.26	2.23
Standard deviation	0.68	0.67	0.67	0.83	0.90	0.80
Range	0.38–3.77	0.42–3.86	0.39–3.95	0.57–4.81	0.51–7.58	0.66–4.71

Table 3 Diagnostic Performance of the Lung Function Questionnaire (LFQ), Pocket Spirometry (PS) and the Combined Strategy (LFQ Followed by the PS) Compared to the Post-Bronchodilation Spirometry (n=235)

Parameters	Lung Function Questionnaire	Pocket Spirometry	Combined
Prevalence, % (95% CI)	24 (19.0–29.8)	24 (19.0–29.8)	34.0 (26.0–43.6)
Sensitivity, % (95% CI)	75.0 (61.6–85.6)	69.6 (55.9–81.2)	78.6 (63.2–89.7)
Specificity, % (95% CI)	55.3 (47.7–62.7)	81.0 (74.5–86.5)	78.8 (68.2–87.1)
Area under the receiver operating characteristics curve	0.65 (0.58–0.72)	0.75 (0.69–0.82)	0.79 (0.71–0.86)
Likelihood ratio (+)	1.68 (1.34–2.10)	3.67 (2.59–5.19)	3.70 (2.36–5.80)
Likelihood ratio (-)	0.45 (0.28–0.73)	0.38 (0.25–0.56)	0.27 (0.15–0.49)
Odds ratio	3.71 (1.91–7.22)	9.78 (4.97–19.20)	13.6 (5.52–33.40)
Positive predictive value, % (95% CI)	34.4 (26.1–43.6)	53.4 (41.4–65.2)	66.0 (51.2–78.8)
Negative predictive value, % (95% CI)	87.6 (80.1–93.1)	89.5 (83.7–93.8)	87.5 (77.6–94.2)

Table 4 Comparison of Lung Function Parameters FEV1, FEV6 or FVC(L) as Measured by Pocket Spirometry, Pre-Bronchodilation and Post-Bronchodilation Gold Standard Spirometry

Lung Function Parameter	Pocket Spirometry	Gold Standard Spirometry
	Pre-Bronchodilator Mean (95% CI)	Pre-Bronchodilator Mean (95% CI)	Post-Bronchodilator Mean (95% CI)
FEV1 (in Liters)	1.74 (1.66–1.82)	1.82 (1.74–1.91)	1.89 (1.80–1.96)
FEV6 or FVC* (in Liters)	2.42 (2.31–2.52)	2.50 (2.39–2.60)	2.55 (2.44–2.65)
Limits of agreement
Values	Limits of agreement	Mean difference	95% CI	p-value
PS FEV1 vs Pre FEV1	−0.288 to 0.499	0.105	0.081 to 0.130	<0.001
PS FEV1 vs Post FEV1	−0.256 to 0.619	0.182	0.153 to 0.210	0.001
PS FEV6* vs Pre FVC	−0.705 to 1.017	0.156	0.102 to 0.211	0.007
PS FEV6* vs Post FVC	−0.683 to 1.124	0.221	0.162 to 0.279	0.434
PS FEV1/FEV6* vs Pre FEV1/FVC	−0.284 to 0.181	−0.052	−0.066 to −0.037	0.000
PS FEV1/FEV6* vs Post FEV1/FVC	−0.284 to 0.202	−0.041	−0.057 to −0.026	0.000

Notes: *FEV₆ for pocket spirometry, FVC for gold standard spirometry.

Figure 2 Bland-Altman plots comparing lung function parameters between pocket spirometry and pre-bronchodilator spirometry. (A) Bland-Altman plot comparing FEV1/FEV6 ratio obtained from pocket spirometry with that FEV1/FVC ratio of pre-bronchodilator spirometry (B) Bland-Altman plot comparing FEV₁ obtained from pocket spirometry with that of pre-bronchodilator spirometry. (C) Bland-Altman plot comparing FEV₆ obtained from pocket spirometry with that of FVC obtained from pre-bronchodilator spirometry.

Hanania NA, Mannino DM, Yawn BP, et al. Predicting risk of airflow obstruction in primary care: validation of the lung function questionnaire (LFQ). Respir Med. 2010;104(8):1160–1170. doi:10.1016/j.rmed.2010.02.009

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