Prognosis

Patients with idiopathic pulmonary fibrosis (IPF) experience progressive dyspnea and functional decline over time. The median survival time has been estimated to be 2-5 years from the time of diagnosis, and most patients will die from their disease.[21][57]​​[64][118]​​ However, the course of the clinical decline differs among patients, with some progressing rapidly, others progressing slowly, and others declining only during acute exacerbations.

Factors associated with a good prognosis:[119][120][121][122][123]

  • "Atypical" high-resolution CT pattern for IPF

  • Stability or improvement in FVC, and/or lung diffusion capacity test over the first 6 months after diagnosis

  • Paradoxically, current cigarette smoking

The effect of smoking may be related to differences in disease severity at presentation among current smokers.[124]

Factors associated with a poor prognosis:[12][15][118][120][122][125][126][127][128][129]​​[130]

  • Advanced age

  • Male sex

  • Severity of FVC impairment

  • Severity of DLCO abnormalities

  • FVC decline in the initial 6-12 months after diagnosis

  • Increased number of fibroblastic foci on lung biopsy

  • Oxyhemoglobin desaturation during an initial 6-minute walk test

  • Failure of the heart rate to recover normally after exercise

  • Acute exacerbations

In one UK cohort study, mortality due to IPF increased by 53% between 2008 and 2018 from 5.2 to 7.9 per 100,000 person-years and was consistently higher for males than females (8.7 vs. 5.3 per 100,000 person-years).[12]

One meta-analysis of placebo controlled trials reported that mortality is lower among patients with mild-moderate disease (78.6 deaths per 1000 patient/years) compared with those with severe disease (188.6 deaths per 1000 patient/years).[130]​ Acute exacerbations pose a significantly increased mortality risk, preceding up to 46% of IPF-related deaths because of the association with rapid deterioration.[15][125]​ The risk of death is increased 4.7-fold when pulmonary fibrosis is present in first-degree relatives.[129]

Multiple prognostic biomarkers have been identified; the clinical utility of these biomarkers is not yet clear.[131][132][133][134]

Prognostic models

The Gender-Age-Physiology (GAP) staging system is an easy-to-calculate and validated prediction tool that can estimate mortality risk in untreated patients.[135][136][137] Its validity in treated patients is being evaluated.[138][139]​​​

The GAP staging system classifies patients into three stages at the time of diagnosis based on:

  • sex (female = 0 vs. male = 1),

  • age (≤60 years = 0; 61-65 years = 1; >65 years = 2),

  • percent predicted forced vital capacity (>75% = 0; 50% to 75% = 1; <50% = 2),

  • percent predicted diffusing lung capacity of carbon monoxide (>55% = 0; 36% to 55% = 1; ≤35% = 2; cannot perform = 3).

The final score estimates the average risk of mortality at 1, 2, and 3 years by disease stage (i.e., score 0-3 = stage 1; score 4-5 = stage 2; score 6-8 = stage 3). Mortality increases with increasing stage and varies depending on the cohort in which the GAP index was validated.

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