Association of RF IgM with high attenuation areas and interstitial lung abnormalities on CT
| RF IgM quartile | Per cent difference (95% CI) in HAA per doubling of RF IgM | p Value | |||||
|---|---|---|---|---|---|---|---|
| <4.03 U/mL | 4.03–8 U/mL | 8.02–17 U/mL | >17 U/mL | p Value for trend | |||
| No. of subjects | 1814 | 1710 | 1616 | 1596 | |||
| HAA, cm3, median (IQR) | 119.2 (100.0 to 144.7) | 120.8 (102.5 to 145.5) | 121.7 (101.5 to 145.4) | 122.8 (103.1 to 147.1) | |||
| Per cent difference (95% CI) in HAA | |||||||
| Unadjusted | 0 (Ref) | 1.56 (−0.39 to 3.55) | 1.16 (−0.81 to 3.16) | 2.58 (0.58 to 4.63) | 0.03 | 0.60 (0.13 to 1.07) | 0.01 |
| Adjusted* | 0 (Ref) | 0.66 (−0.88 to 2.22) | 0.67 (−0.89 to 2.26) | 2.10 (0.50 to 3.72) | 0.01 | 0.49 (0.11 to 0.86) | 0.01 |
| Never smoker | 0 (Ref) | 0.54 (−1.74 to 2.86) | 1.04 (−1.31 to 3.46) | 0.82 (−1.61 to 3.30) | 0.59 | 0.15 (−0.44 to 0.75) | 0.62 |
| Ever smoker | 0 (Ref) | 1.30 (−0.79 to 3.42) | 0.88 (−1.21 to 3.01) | 3.53 (1.41 to 5.70) | 0.001 | 0.81 (0.33 to 1.30) | 0.001 |
| Prevalence ratio (95% CI) for ILA per doubling of RF IgM | |||||||
| No. of subjects | 636 | 652 | 578 | 537 | |||
| ILA prevalence, % (95% CI) | 12.0 (9.6 to 14.7) | 10.7 (8.6 to 13.4) | 12.3 (9.8 to 15.2) | 16.0 (13.2 to 19.4) | |||
| Prevalence ratio (95% CI) for ILA | |||||||
| Unadjusted | 1 (Ref) | 0.90 (0.66 to 1.22) | 1.03 (0.76 to 1.39) | 1.34 (1.01 to 1.78) | 0.007 | 1.10 (1.02 to 1.17) | 0.009 |
| Adjusted† | 1 (Ref) | 0.89 (0.66 to 1.20) | 0.97 (0.72 to 1.30) | 1.21 (0.91 to 1.60) | 0.049 | 1.07 (0.998 to 1.15) | 0.057 |
| Never smoker | 1 (Ref) | 0.92 (0.59 to 1.41) | 0.85 (0.54 to 1.34) | 0.81 (0.51 to 1.30) | 0.43 | 0.97 (0.86 to 1.09) | 0.60 |
| Ever smoker | 1 (Ref) | 0.90 (0.60 to 1.36) | 1.10 (0.75 to 1.61) | 1.61 (1.12 to 2.32) | 0.001 | 1.14 (1.05 to 1.24) | 0.002 |
*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 IgM and smoking was 0.09 in the HAA analysis and 0.04 in the ILA analysis.
HAA, high attenuation areas; ILA, interstitial lung abnormalities; RF, rheumatoid factor.