TABLE 2.
Risk factors for the progression of non-idiopathic pulmonary fibrosis interstitial lung diseases (ILDs)
| Risk factor | First author (year) [ref.] | Hazard ratio (95% CI) | p-value |
| General risk factors | |||
| UIP | Flaherty (2019) [2] | 1.53 (−0.68–3.74) | NA |
| BMI | Alakhras (2007) [19] | 0.93 (0.89–0.97) | 0.002 |
| Oxygen desaturation during 6MWT# | Alfieri (2020) [20] | OR¶ 8.7 (4.42–17.3) | NA |
| Disease | |||
| Fibrotic hypersensitivity pneumonitis | Gimenez (2018) [21] | ||
| Decline in FVC by ≥10% | Gimenez (2018) [21] | 4.13 (1.96–8.70) | 0.005 |
| Lower baseline FVC % | Gimenez (2018) [21] | 1.03 (1.01–1.05) | 0.003 |
| Antigen identification | Gimenez (2018) [21] | 0.18 (0.04–0.77) | 0.021 |
| MUC5B+/TLD+ (gene variants) | Ley (2019) [22] | 3.52 (1.87–6.62) | 0.00009 |
| Rheumatoid arthritis-ILD | Zamora-Legoff (2017) [9] | ||
| UIP versus NSIP | Zamora-Legoff (2017) [9] | 3.29 (1.28–8.41) | 0.013 |
| High levels of CCP antibody/anti-CCP2 titres+ | Khan (2021) [23] | 1.05 (1.01–1.10) | 0.01 |
| Smoking, 30 pack-years | Kronzer (2021) [24] | OR¶ 6.06 (2.72–13.5) | NA |
| Fibrotic score on HRCT | Solomon (2016) [25] | 1.02 (1.01–1.03) | 0.0002 |
| Extent of fibrosis on HRCT | Solomon (2016) [25] | 1.12 (1.08–1.17) | <0.000006 |
| Systemic sclerosis | Goh (2017) [26] | ||
| Low baseline FVC <65% and low baseline DLCO ≤55% | Sánchez-Cano (2018) [27]; Hoffmann-Vold (2019) [28] | OR¶ 1.02 (1.01–1.03) | <0.001 |
| Decline in DLCO >15% | Le Gouellec (2017) [29] | 2.03 (1.25–3.29) | <0.005 |
| Decline in KCO >10% | Goh (2017) [26] | 2.35 (1.40–3.95) | <0.001 |
| Fibrotic score on HRCT | Ibrahim (2020) [30] | 2.52 (1.16–5.49) | 0.02 |
| Extent of fibrosis on HRCT (HRCT extent 10–30% and FVC <70%) | Goh (2008) [31] | 3.46 (2.19–5.46) | <0.0005 |
UIP: usual interstitial pneumonia; BMI: body mass index; 6MWT: 6-min walk test; NA: not available; FVC: forced vital capacity; NSIP: non-specific interstitial pneumonia; CCP: cyclic citrullinated peptide; HRCT: high-resolution computed tomography; DLCO: diffusing capacity of the lung for carbon monoxide; KCO: transfer coefficient of the lung for carbon monoxide. #: 6MWT correlates to some extent with DLCO levels, but should not be strictly viewed as a surrogate marker [32]; ¶: hazard ratio for the risk factor was not available in the literature; hence, odds ratio was considered; +: usefulness of assessing anti-citrullinated peptide antibody levels merits future research as this study was done only in women.