Relationship between silicosis diagnosis (outcome measure) and respiratory function tests for secondary screening participants
| No silicosis | Confirmed silicosis | No silicosis (ref) versus confirmed silicosis* | Simple silicosis | Complicated silicosis | Simple (ref) versus complicated silicosis | |
| N=297 | N=117 | OR (95% CI) | N=96 | N=21 | OR (95% CI) | |
| FEV1† | ||||||
| Percentage of predicted, mean(SD) | 98.0 (14.4) | 93.3 (18.0) | 0.98 (0.96 to 0.99) | 95.9 (16.9) | 81.1 (18.4) | 0.96 (0.93 to 0.99) |
| z-score, median (P25, P75) | −0.2 (–0.8, 0.6) | −0.3 (–1.3, 0.5) | 0.77 (0.63 to 0.95) | −0.1 (–0.9,0.5) | −1.7 (–2.3,–0.2) | 0.56 (0.36 to 0.87) |
| FVC† | ||||||
| Percentage of predicted, mean (SD) | 101.9 (13.2) | 98.3 (16.0) | 0.98 (0.96 to 1.00) | 100.6 (14.4) | 87.5 (19.2) | 0.95 (0.91 to 0.99) |
| z-score, median (P25, P75) | 0.3 (–0.6, 0.8) | 0.0 (–0.9, 0.7) | 0.79 (0.64 to 0.98) | 0.2 (–0.7,0.8) | −1.2 (–2.1,–0.1) | 0.52 (0.32 to 0.84) |
| FEV1/FVC† | ||||||
| Percentage of predicted, mean (SD) | 95.9 (7.8) | 94.7 (10.9) | 0.98 (0.95 to 1.01) | 95.1 (11.1) | 92.8 (9.9) | 0.99 (0.94 to 1.04) |
| z-score, median (P25, P75) | −0.4 (–1.1, 0.1) | −0.7 (–1.5,0.3) | 0.88 (0.70 to 1.10) | −0.5 (–1.6,0.3) | −1.1 (–1.5,–0.3) | 0.88 (0.59 to 1.33) |
| DLco† | ||||||
| Percentage of predicted, mean (SD) | 104.2 (17.9) | 94.9 (19.4) | 0.98 (0.97 to 0.99) | 99.0 (16.3) | 76.0 (21.8) | 0.92 (0.87 to 0.96) |
| z-score, median (P25, P75) | 0.3 (–0.5, 1.0) | −0.4 (–1.2,0.4) | 0.75 (0.62 to 0.93) | −0.3 (–1.0,0.5) | −2.1 (–2.6,–0.4) | 0.31 (0.16 to 0.59) |
| Reduced DLco (<LLN), n (column %) | ||||||
| No | 229 (93.8) | 83 (86.5) | Ref | 77 (97.5) | 6 (35.3) | Ref |
| Yes | 15 (6.2) | 13 (13.5) | 1.80 (0.78 to 4.15) | 2 (2.5) | 11 (64.7) | 76.6 (10.7 to 546.14) |
| Respiratory function patterns‡, n (column %) | ||||||
| Normal | 206 (84.4) | 65 (67.7) | Ref | 57 (72.1) | 8 (47.1) | Ref |
| Restrictive | 10 (4.1) | 11 (11.5) | 3.03 (1.13 to 8.12) | 4 (5.1) | 7 (41.2) | 13.18 (2.64 to 65.86) |
| Obstructive | 26 (10.7) | 17 (17.7) | 2.29 (1.10 to 4.77) | 15 (19.0) | 2 (11.7) | 0.87 (0.15 to 4.97) |
| Mixed | 2 (0.8) | 3 (1.2) | 5.43 (0.83 to 35.6) | 3 (3.8) | 0 (0) | – |
*RFT data missing for 74 patients.
†Normal=FEV1/FVC ratio ≥LLN and FVC≥LLN; Restrictive=FEV1/FVC ratio ≥LLN and FVC<LLN; obstructive=FEV1/FVC ratio <LLN and FVC≥LLN; mixed=FEV1/FVC ratio <LLN and FVC<LLN.19
‡Adjusted for age, BMI, smoking and country of birth. FEV1, FVC, FEV1/FVC and DLco not adjusted for age.
BMI, body mass index; DLco, diffusion capacity for carbon monoxide; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; LLN, lower limit of normal.