Comparison of mortality risk scoring systems in idiopathic pulmonary fibrosis
| Variables | Predictive value | Advantages | Disadvantages | |
| Composite physiologic index (CPI) [9] | DLCO % pred FVC % pred FEV1 % pred Correlation with morphologic extent: CPI=91.0−(0.65×DLCO)−(0.53×FVC)+(0.34 FEV1) | More accurate predictor of mortality than individual functional variables | Correction for confounding effects of emphysema | Retrospective data; measurement variability in DLCO; not yet been replicated |
| Du Bois et al. model [7] | Age (0–8 pts) 24-week history of respiratory hospitalisation (0 or 14 pts) FVC % pred (0–18 pts) 24-week change in FVC (0–21 pts) | 1-year mortality risk Examples total score: • 0–4 pts: <2% • 22–29 pts: 10–20% • 38–40 pts: 40–50% • >50 pts: >80% | Easily and reliably evaluable; longitudinal variables | Assessed in cohorts with only mild to moderate physiological impairment at baseline and with exclusion of severe emphysema |
| Gender–age–physiology (GAP) model [82] | Gender (0–1 pts) Age (0–2 pts) FVC % pred (0–2 pts) DLCO % pred (0–3 pts) | Cumulative mortality at 1, 2, 3 years Examples 1-year mortality risk: Stage I (0–3 pts): 6% Stage II (4–5 pts): 16% Stage III (6–8 pts): 39% | Externally validated GAP calculator as add-on tool for more precise estimation of risk | Retrospective data; possible referral bias (academic centres); tends to overestimate risk |
| Longitudinal GAP model [83] | Gender (0–1 pts) Age (0–4 pts) FVC % pred (0–15 pts) 24-week relative change in FVC (0–12 pts) DLCO % pred (0–23 pts) Respiratory hospitalisation (last 24 weeks) (0 or 14 pts) | 1 and 2-year mortality risk Examples 1-year mortality risk: • 0–10 pts: <2% • 27–34 pts: 10–20% • 43–45 pts: 40–50% • 55–60 pts: ≥80% | Longitudinal risk assessment; prospective data | No external validation |
| CT-GAP model [8] | Gender Age FVC % pred Semi-quantitative CT fibrosis score | Cumulative mortality at 1, 2, 3 years Examples 1-year mortality risk: Stage I (0–3 pts): 5% Stage II (4–5 pts): 19% Stage III (6–8 pts): 43% | Accuracy comparable to that of the original GAP model; alternative model when DLCO unmeasurable or not available; externally validated | Retrospective data; requires expertise in quantification of CT disease extent |
DLCO: diffusing capacity of carbon monoxide; FVC: forced vital capacity; FEV1: forced expiratory volume in 1 s; CT: computed tomography; % pred: % predicted; pts: points. Reproduced and modified from [89] with permission from the publisher.