COPD Causation and Workplace Exposures: An Assessment of Agreement among Expert Clinical Raters

Figures & data

Table 1.  Attribution of causation by Physician Case Raters

	Case Scenarios						Causal Attribution by Raters
Exposure Grouping	Case Number	Age	Pack-years	Occupational exposure/duration	FEV1% predicted	Other information	Smoking% (Median, IQR)	Occupation% (Median, IQR)	Other% (Median, IQR)
High Smoking	1	67	65	Scrap metal work 14 years	33		80 (70–90)	10 (10–27)	0 (0–10)
High				Foundry work 19 years
Occupational				Painter 10 years
	4	78	61	Fireman 40 years	29	PiMZ AAT	80 (60–86.3)	15 (10–22.5)	0 (0–20)
High Smoking				Welder 25 years	78	Pleural plaques	70 (63.8–81)	22.5 (15.8–30)	0 (0–10)
Medium	7	68	60	Construction labourer
Occupational				2 years
	10	74	62	Farmer 4 years	26		70 (60–80)	25 (20–40)	0 (0–0)
				Cadmium smelter 40 years
High Smoking	3	66	61	Grain dust exposure 9 years	60		90 (80–96.3)	6 (0–11.3)	0 (0–2.5)
Low
Occupational
Medium Smoking	11	50	25	Wood turner 34 years	51		50 (35–75)	40 (10–60)	0 (0–5)
High
Occupational
	14	57	21	Plater/welder 42 years	74	Angina	60 (40–90)	20 (10–40)	0 (0–20)
Medium Smoking	8	74	25	Scrap metal work 3 years	26		67.5 (50–80)	32.5 (17.5–42.5)	0 (0–2.5)
Medium				Cotton carder 25 years
Occupational
	12	42	24	Collier (coal) 24 years	72		60 (50–85)	30 (15–50)	0 (0–5)
Medium Smoking	6	59	19	Labourer construction 9 years	31	PiZZ AAT	30 (20–50)	5 (0–10)	65 (45–78)
Low
Occupational
Low Smoking	2	62	14	Labourer construction 6 years	67	Silicotic changes on radiology	30 (20–60)	70 (30–80)	0 (0–12.5)
High
Occupational				Stonemason 39 years
	13	50	15	Fettler (silica) 32 years	53	Silicotic changes on radiology	45 (40–60)	50 (40–60)	0 (0–0)
Low Smoking	9	86	14	Foundry work 25 years	37	Previous MI	33 (20–61.3)	37.5 (10–66.8)	0 (0–30)
Medium
Occupational
	15	38	11	Baker 20 years	74		50 (31–82.5)	30 (0–60)	0 (0–27.5)
Low Smoking	5	71	10	Biomass fuel/indoor cooking	49		20 (10–50)	45 (0–76)	20 (0–80)
Low Occupational				in Peru 8 years

Table 2.  Annual decline in lung function (FEV₁), rated concern level, and workplace advice for cases 11—15

Case No.	Baseline FEV1 (L)	∆FEV1 (ml/y) (%/year)	Raters response Concerned by rate of decline?			Suggested action
11*	2.30	–95	Yes	17		Leave work	9	2 OCC
		over 4 years	No	1	(OCC)	Alter work	8	6 OCC
		(4.13%)	DK	1	(OCC)	Other	2	1 OCC
12*	3.40	–167	Yes	18		Leave work	8	8 OCC
		over 3 years	No	1	(COPD)	Alter work	7	7 OCC
		(4.9%)	DK			Other	4	4 OCC
13*	2.40	–400	Yes	17		Leave work	6	6 OCC
		over 1 year	No	1	(OCC)	Alter work	8	8 OCC
		(16%)	DK	1	(COPD)	Other	5	5 OCC
14	3.10	–105	Yes	14		Leave work	4	4 OCC
		over 4 years	No	4	(3 COPD, 1 OCC)	Alter work	8	8 OCC
		(3.4%)	DK	1	(COPD)	Other	7	7 OCC
15	2.98	–150	Yes	16		Leave work	4	4 OCC
		over 2 years	No	3	(3 OCC)	Alter work	8	8 OCC
		(5.0%)	DK			Other	7	7


*Deemed significant detectable decline as per Figure 1 (13) assuming within-person variation of 4%.

DK; don't know.

OCC; occupational respiratory expert rater.

COPD; COPD expert rater.

Figure 1.  Detectable excess rate of decline in FEV₁ (%/year) by relative within-person variation and duration of follow-up (1–15 years). Indicated are two recommended limits (two vertical lines) based on monitoring programs with good data quality (within-person variation of 4%) and by the ACOEM (within person variation of 6%). FEV₁ = forced expiratory volume in 1 second).

Table 3.  Estimates from the linear regression analysis for predicting the proportion of occupational causation rated (%) in each case

					95% confidence interval for β
Explanatory variables	β coefficient (unit is%)	S. E.	t-value	p-value	Lower limit	Upper limit
Intercept	26.35	3.86	6.83	0.000	18.75	33.95
Weighted occupational exposure^†	0.28	0.06	4.87	0.000	0.17	0.40
Pack-years	–0.52	0.07	–7.78	0.000	–0.65	–0.39
Rater type, COPD expert^‡	9.39	2.71	3.47	0.001	4.06	14.72


^† Duration of exposure weighted by intensity of exposure.

^‡COPD expert (value 1) compared to OLD expert (value 0).

Table

Medical History
50-year-old man
No symptoms and no GP respiratory consultations, picked up on regular health surveillance as works in dusty environment
Smoking History
Ex-smoker; 16-36 years old, 25 cigarettes per day; 25 pack years
Previous Medical History	Family History
Nil	Nil
Current Medication	Allergies
None	Nil known
Occupational History
Job Title	Age	Duration	Self Reported VFDG*	Exposure
Wood machining apprentice	16-23	7	Yes	Woods
Wood turner	23-current	27	Yes	Heavy dust exposure to soft and hard woods, no extraction ventilation, no mask usage
Current Pulmonary Function
Measure		Actual	Predicted	%Predicted
FEV1 litres		1.92	3.80	50.5
FVC litres		2.98	4.73	63.0
FEV1/FVC		0.64	–	–
TLCO		8.2	10.67	76.9
No increase in normal diurnal variation on serial PEF measures over 3 weeks
No airway hyper-responsiveness. SpO2 98% at rest breathing room air
Alpha 1 antitrypsin		CXR	HRCT
Normal, PiMM genotype		Normal	Not Done
Annual FEV1
Measured FEV1	Litres
Most recent	1.92
1 year previous	2.02
2 years previous	2.11
3 years previous	2.23
4 years previous	2.30