A Novel Case-Finding Instrument for Chronic Obstructive Pulmonary Disease in Low- and Middle-Income Country Settings

Figures & data

Figure 1 Odds of COPD by risk factor. Unadjusted odds of COPD by risk factor with 95% CI.

Table 1 Derived COLA Score

Symptoms/Functional Score
	Have you had whistling/wheezing in chest in last 12 months	1
	Have you brought up phlegm from your chest on most days or nights of the week during at least 3 months in at least 2 years?	1
	Have you ever been woken up from sleep by wheezing?	1
	In the past 12 months, have you had to miss work or have your daily activities been impeded because of your respiratory problems?	1
	In the past 12 months, have you been hospitalized because of respiratory problems?	1
	Do you currently smoke?	1
	Do you use biomass fuel daily?	1
Age score
	< 55 years	0
	≥ 55 years	1
Peak expiratory flow score
	≥ 400 L/min	0
	250–399 L/min	1
	< 250 L/min	2

Table 2 Baseline Characteristics of 1,173 LiNK Study Participants with Complete Respiratory Symptom Data

Variables		N	COPD (n = 53)	No COPD (n = 1,120)	P-value
Socio-demographics		1173
Age, in years: Mean ± SD		1173	54.1 (12.2)	46.7 (10.3)	<0.01
Sex: Female		622	20 (37.7%)	602 (53.8%)	0.03
Head of house: Yes		855	46 (86.8%)	809 (72.3%)	0.03
Working: Yes		1066	47 (88.7%)	1019(91.1%)	0.72
Marital status, n (%)		1173			0.63
	Single	150	7 (13.2%)	141 (12.6%)
	Married	742	35 (66%)	706 (63.1%)
	Cohabiting	67	2 (3.8%)	64 (5.8%)
	Separated/Divorced	93	2 (3.8%)	90 (8.1%)
	Widow/Widower	108	7 (13.2%)	101 (9%)
Household characteristics
Household size, median (IQR)		1173	4 (2, 6)	5 (3, 7)	0.32
Has chimney, n (%)		243	17 (32.1%)	226 (20.3%)	0.06
Current Biomass use, n (%)		1140	53 (100%)	1087 (97.1%)	0.40
Cooking location, n (%)					0.07
	Outside the house	576	23 (43.4%)	553 (49.4%)
	Inside the main living area	102	1 (1.9%)	101 (9%)
	In a separate room/hut	494	29 (54.7%)	465 (41.6%)
Fuel source					<0.01
	Wood	690	44 (83%)	646 (57.7%)
	Coal	450	9 (17%)	441 (39.4%)
	Other	33	0 (0)	33 (2.9%)
Smoking status
	Daily Smoker	97	10 (18.9%)	87 (7.8%)	0.01
	Pack-years: Median (IQR)	1173	0 (0, 1.5)	0 (0, 0)	<0.01
	Pack-years: Mean ± SD	1173	2.1 (4.8)	0.8 (3.6)	0.01
Lung function, median z-score (IQR)
	Pre-bronchodilator FEV	1173	−1.95 (−2.30,-1.60,)	−0.30 (−0.37,-0.24)	<0.01
	Pre-bronchodilator FVC	1173	−0.57 (−1.00,-0.15)	−0.27 (−0.33,-0.20)	0.07
	Pre-bronchodilator FEV/FVC ratio	1173	−3.43 (−3.85,-3.00)	−0.10 (−0.15),-0.04	<0.01
	Peak Expiratory Flow	1173	290 (258, 322)	432 (426, 439)	<0.01
Body mass index, mean (SD)		1173	21.8 (4.7)	24.9 (5)	<0.01
History of pulmonary tuberculosis, n (%)		1173	7 (15.2%)	30 (3%)	<0.01

Figure 2 Calibration of generated model on test set. Log odds of COPD compared to 5-point respiratory symptom and exposure selection, age and PEF from random forest analysis with best-fit line.

Table 3 Operating Characteristics by COLA Score

Score	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)	PLR
COLA ≥ 2	96	41	7	100	1.6
COLA ≥ 3	70	81	15	98	3.7
COLA ≥ 4	43	96	32	97	9.9
COLA ≥ 5	19	99	50	96	21.1

Abbreviations: PPV, positive predictive value; NPV, negative predictive value ; PLR, positive likelihood ratio.

Figure 3 Risk factors for COPD and diagnostic accuracy of demographic and respiratory questionnaires alone, peak expiratory flow (PEF) alone and combined questionnaires with PEF. Odds of COPD (left panel) stratified by age and symptom score, PEF and combined age, symptoms/exposure score and PEF with 95% CI. Area under the curve (AUC) for COPD (right panel) stratified by age and symptom score, PEF and combined age, symptoms score and PEF with 95% CI.