Patient characteristics in this study*
| Parameters | AE-IIPs (n=28) | AE-IPF (n=8) | AE-non-IPF (n=20) | P value |
| Stable state | ||||
| Sex, male/female | 21/7 | 8/0 | 13/7 | 0.0749 |
| Smoking, yes/no | 19/9 | 7/1 | 12/8 | 0.2144 |
| mMRC, ≤1/≥2 | 10/18 | 3/5 | 7/13 | 1.0000 |
| Stage, I–III/IV | 17/11 | 4/4 | 13/7 | 0.6715 |
| LTOT before AE, yes/no | 11/17 | 4/4 | 7/13 | 0.6175 |
| Prednisolone before AE, yes/no | 9/19 | 2/6 | 7/13 | 1.0000 |
| Antifibrotic drugs, yes/no | 5†/23 | 2‡/6 | 3§/17 | 0.6056 |
| At the time of diagnosis of AE | ||||
| Age, years | 74.5 (69.75–79.0) | 74.5 (69.5–78.25) | 74.5 (69.75–84.0) | 0.7405 |
| HRCT pattern, diffuse/non-diffuse | 12/16 | 4/4 | 8/12 | 0.6908 |
| PaO2/FiO2 ratio, ≤200/>200 | 17/11 | 6/2 | 11/9 | 0.4188 |
| WCC, /μL | 10 150 (9050–12 950) | 10 300 (9000–14 400) | 10 150 (9250–12 950) | 0.9594 |
| LDH, U/L | 317.0 (245.5–404.5) | 296.5 (246.5–414.25) | 341.0 (245.5–403.75) | 0.9797 |
| KL-6, U/mL | 1196 (889–2,142) | 1024.5 (889.5–1394) | 1346 (849.75–2359) | 0.3091 |
| CRP, mg/dL | 12.38 (5.07–14.28) | 5.455 (0.38–12.56) | 2.982 (0.871–9.815) | 0.8787 |
| FDP, 10</≥10 mg/L | 21/7 | 4/4 | 17/3 | 0.1423 |
| 90-day survival, yes/no | 19/9 | 6/2 | 13/7 | 1.0000 |
*Each parameter was compared between the AE-IPF and AE-non-IPF groups using Fisher’s exact test or the Wilcoxon rank-sum test.
†Pirfenidone (n=4) and nintedanib (n=1).
‡Pirfenidone (n=1) and nintedanib (n=1).
§Pirfenidone (n=3) and nintedanib (n=0).
AE, acute exacerbation; CRP, C reactive protein; FDP, fibrin degradation product; FiO2, fraction of inspired oxygen; HRCT, high-resolution CT; IIPs, idiopathic interstitial pneumonias; IPF, idiopathic pulmonary fibrosis; KL-6, Krebs von den Lungen-6; LDH, lactate dehydrogenase; LTOT, long-term oxygen therapy; mMRC, modified medical research council score; PaO2, arterial oxygen tension; WCC, white blood cell count.