Table 1. Clinical characteristics of patients with IIP.
| Variable | Total IIP | IPF | Non-IPF | P value |
|---|---|---|---|---|
| Subjects (n) | 100 | 30 | 70 | |
| Age (years) | 70±1 | 70±1 | 71±1 | 0.781 |
| Gender (M/F) | 72/28 | 26/4 | 46/24 | 0.050 |
| Autoantibodies* (+/−) | 51/49 | 15/15 | 35/35 | 1.000 |
| Smoker (+/−) | 68/32 | 25/5 | 43/27 | 0.037 |
| Brinkman index | 602±62 | 739±106 | 544±75 | 0.136 |
| Corticosteroid (%) | 28.0 | 30.0 | 27.1 | 0.810 |
| Duration of corticosteroid treatment (days) | 322±71 | 274±109 | 343±91 | 0.917 |
| Immunosuppressive reagents (%) | 12.0 | 13.3 | 11.4 | 0.749 |
| Duration of immunosuppressive reagent treatment (days) | 149±70 | 116±92 | 163±80 | 0.894 |
| NAC (%) | 11.0 | 23.3 | 5.7 | 0.016 |
| Duration of NAC treatment (days) | 120±44 | 178±86 | 95±51 | 0.015 |
| Raynaud’s phenomenon (%) | 4.0 | 3.3 | 4.3 | 1.000 |
| Arthralgia (%) | 9.0 | 10.0 | 8.6 | 1.000 |
| Morning stiffness (%) | 8.0 | 6.7 | 8.6 | 1.000 |
| Dry mouth/eye (%) | 22.0 | 13.3 | 25.7 | 0.199 |
| Rash (%) | 5.0 | 3.3 | 5.7 | 1.000 |
| Muscle weakness (%) | 4.0 | 0.0 | 5.7 | 0.313 |
| WBC (/μL) | 7,826±285 | 8,253±548 | 7,643±334 | 0.244 |
| LDH (IU/L) | 251±8 | 245±10 | 253±11 | 0.813 |
| CK (U/L) | 118±14 | 99±23 | 127±18 | 0.039 |
| CRP (mg/dL) | 0.60±0.14 | 0.63±0.23 | 0.59±0.18 | 0.279 |
| ESR (mm/h) | 16±1 | 15±2 | 17±2 | 0.428 |
| ALD (U/L) | 5.9±0.4 | 6.0±0.4 | 5.9±0.6 | 0.400 |
| BNP (pg/mL) | 50.7±10.5 | 31.6±5.8 | 61.8±16.0 | 0.555 |
| KL-6 (U/mL) | 1,122±83 | 1,135±99 | 1,117±112 | 0.177 |
| SP-A (ng/mL) | 74.3±4.3 | 76.7±6.8 | 73.3±5.4 | 0.350 |
| SP-D (ng/mL) | 228.8±16.0 | 248.2±22.7 | 220.7±20.6 | 0.083 |
| VC (L) | 2.7±0.1 | 2.7±0.1 | 2.6±0.1 | 0.857 |
| %VC (%) | 82.1±2.3 | 80.1±3.8 | 83.1±2.9 | 0.544 |
| TSH (μIU/mL) | 2.59±0.30 | 2.83±0.75 | 2.49±0.30 | 0.904 |
| FT4 (ng/dL) | 1.17±0.18 | 1.17±0.04 | 1.16±0.02 | 0.609 |
| FT3 (pg/mL) | 2.84±0.04 | 2.95±0.06 | 2.80±0.06 | 0.150 |
| TgAb (IU/mL) | 55.09±13.62 | 42.48±22.83 | 60.57±16.90 | 0.134 |
| TPOAb (IU/mL) | 34.58±9.84 | 27.89±19.84 | 37.45±11.27 | 0.015 |
| TSH (low/high/normal) | 2/7/91 | 1/3/26 | 1/4/65 | 0.600 |
| FT4 (low/normal) | 5/95 | 2/28 | 3/67 | 0.635 |
| FT3 (low/normal) | 11/89 | 0/30 | 11/59 | 0.031 |
| TgAb positive (%) | 17.0 | 16.7 | 17.4 | 1.000 |
| TPOAb positive (%) | 16.0 | 10.0 | 18.6 | 0.379 |
| TRAb positive (%) | 0.0 | 0.0 | 0.0 | 1.000 |
| TgAb or TPOAb positive (%) | 22.0 | 16.7 | 24.3 | 0.445 |
| Subclinical hyperthyroidism (%) | 2.0 | 3.3 | 1.4 | 0.512 |
| Subclinical hypothyroidism (%) | 6.0 | 6.7 | 5.7 | 1.000 |
| Low T3 syndrome (%) | 11.0 | 0.0 | 15.7 | 0.031 |
| Hyperthyroidism (%) | 0.0 | 0.0 | 0.0 | 1.000 |
| Hypothyroidism (%) | 1.0 | 3.3 | 0.0 | 0.300 |
*, anti-nuclear antibody, rheumatoid factor, anti-double stranded DNA antibody, anti-SSA antibody, anti-SSB antibody, anti-U1 ribonucleoprotein antibody, anti-cyclic citrullinated peptide antibody, anti-topoisomerase antibody, anti-smith antibody, anti-aminoacyl tRNA synthetase antibody, anti-centromere antibody, myeloperoxidase-anti-neutrophil cytoplasmic antibody, proteinase 3-anti-neutrophil cytoplasmic antibody. P value: IPF vs. non-IPF. Mean ± SEM. +, positive; −, negative. NAC, inhalation of N-acetylcysteine; WBC, white blood cell; LDH, lactate dehydrogenase; CK, creatine kinase; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; ALD, aldolase; BNP, brain natriuretic peptide; KL-6, Krebs von den lungen-6; SP-A, surfactant protein-A; SP-D, surfactant protein-D; VC, vital capacity; TSH, thyroid stimulating hormone; FT4, free thyroxine; FT3, free triiodothyronine; TgAb, thyroglobulin antibody; TPOAb, thyroid peroxidase antibody.