Association of RF IgA with high attenuation areas and interstitial lung abnormalities on CT
| RF IgA quartile | Per cent difference (95% CI) in HAA per doubling of RF IgA | p Value | |||||
|---|---|---|---|---|---|---|---|
| <6.04 U/mL | 6.04–9 U/mL | 9.04–15.86 U/mL | >15.86 U/mL | p Value for trend | |||
| No. of subjects | 1969 | 1554 | 1529 | 1684 | |||
| HAA, cm3, median (IQR) | 116.6 (99.0 to 142.5) | 119.9 (101.7 to 143.0) | 123.6 (102.9 to 148.1) | 124.5 (105.2 to 149.2) | |||
| Per cent difference (95% CI) in HAA | |||||||
| Unadjusted | 0 (Ref) | 1.99 (0.03 to 3.99) | 5.15 (3.11 to 7.22) | 6.26 (4.25 to 8.30) | <0.001 | 1.65 (1.10 to 2.21) | <0.001 |
| Adjusted* | 0 (Ref) | 1.73 (0.15 to 3.33) | 2.18 (0.57 to 3.82) | 3.25 (1.65 to 4.88) | <0.001 | 0.95 (0.50 to 1.40) | <0.001 |
| Never smoker | 0 (Ref) | 1.96 (−0.37 to 4.35) | 1.02 (−1.37 to 3.46) | 2.58 (0.12 to 5.09) | 0.09 | 0.55 (−0.17 to 1.29) | 0.14 |
| Ever smoker | 0 (Ref) | 1.59 (−0.53 to 3.76) | 3.46 (1.29 to 5.69) | 4.35 (2.23 to 6.52) | 0.001 | 1.35 (0.78 to 1.92) | <0.001 |
| Prevalence ratio (95% CI) for ILA per doubling of RF IgA | |||||||
| No. of subjects | 747 | 617 | 516 | 523 | |||
| ILA prevalence, % (95% CI) | 9.6 (7.7 to 12.0) | 12.5 (10.1 to 15.3) | 13.6 (10.9 to 16.8) | 16.1 (13.2 to 19.5) | |||
| Prevalence ratio (95% CI) for ILA | |||||||
| Unadjusted | 1 (Ref) | 1.29 (0.96 to 1.75) | 1.41 (1.03 to 1.92) | 1.67 (1.24 to 2.24) | 0.001 | 1.15 (1.08 to 1.23) | <0.001 |
| Adjusted† | 1 (Ref) | 1.24 (0.92 to 1.68) | 1.26 (0.93 to 1.71) | 1.42 (1.05 to 1.91) | 0.038 | 1.11 (1.03 to 1.20) | 0.006 |
| Never smoker | 1 (Ref) | 0.96 (0.60 to 1.51) | 0.88 (0.55 to 1.40) | 1.15 (0.73 to 1.82) | 0.46 | 1.04 (0.88 to 1.23) | 0.68 |
| Ever smoker | 1 (Ref) | 1.49 (0.99 to 2.22) | 1.67 (1.11 to 2.52) | 1.62 (1.09 to 2.42) | 0.001 | 1.14 (1.05 to 1.23) | 0.001 |
*Adjusted for age, sex, race, study site, BMI, waist circumference, pack-years of smoking, current smoking status, total volume of imaged lung, per cent emphysema and tube current.
†Adjusted for age, sex, race, pack-years of smoking and current smoking status.
p Value for interaction of RF IgA and smoking was 0.15 in the HAA analysis and 0.31 in the ILA analysis.
HAA, high attenuation areas; ILA, interstitial lung abnormalities; RF, rheumatoid factor.