Pulmonary fibrosis (PF), a disease that affects the respiratory system, is characterized by the thickening and stiffening of lung tissue, leaving scar tissue in the process. There are many factors that can affect survival in PF patients.
Most PF cases are classified as idiopathic pulmonary fibrosis (IPF), meaning that the underlying cause is not known. Instead, there may be a number of potential reasons that contribute to disease development, such as occupational and environmental exposure to pollutants, specific medication or drugs, radiation therapy, some connective tissue diseases, and interstitial lung disease.
PF has a generally poor prognosis. Median survival for PF patients is between 2.5 and 3.5 years from the time of diagnosis, although some patients live much longer than that. The most common cause of death is respiratory failure.
A series of risk factors have an impact on the prognosis of patients with PF. These include ethnicity, smoking, dyspnea (shortness of breath), the physical features of the patient, other illnesses, age, and gender. A number of predictors can be used to estimate prognosis in PF such as radiographic, physiologic, pathologic, and biomarker predictors.
Ethnicity
Limited data is available on the role of ethnicity in the prognosis of PF, but a number of studies suggest that white people are more likely to be diagnosed with PF than blacks, and that age-adjusted mortality rate in Hispanics is lower than in whites.
Smoking
The effects of smoking on survival in PF have been variable. While some studies had suggested there would be a survival advantage in current smokers compared to former and non-smokers, a recent study has demonstrated this survival advantage was not significant after adjusting for disease severity.
Dyspnea
In PF, the Medical Research Council (MRC) chronic dyspnea score at baseline and the clinical radiographic-physiologic (CRP) dyspnea score at baseline, together with changes in score at six and 12 months, have been shown to be significant independent predictors of survival.
Physical features
Physical exam findings such as clubbing of the fingers and toes and body mass index (BMI) have been shown to be associated with prognosis in IPF.
Other illnesses
Common comorbidities (or other illnesses) in IPF patients include pulmonary hypertension (PH), emphysema, gastroesophageal reflux disease (GERD), coronary artery disease, and bronchogenic carcinoma. These illnesses have been found to be associated with an increased risk of death in patients with IPF.
Age
Older age is a clinical feature of PF, with a median age of 66 years at the time of diagnosis, and older age has been linked to a poorer prognosis in PF. Emerging data has suggested that age-related changes in cellular function may play key roles in the course of PF.
Gender
IPF is more common in men, but gender differences in survival have been inconsistent. Studies suggest females have a significant survival advantage after adjusting for age, smoking status and physiologic variables, however, mortality rates in women with pulmonary fibrosis are climbing more rapidly than in men.
Radiographic predictors
High-resolution computed tomography (HRCT) of the chest has become the radiographic standard in the evaluation of PF. Reticulation and honeycombing are often combined to reach an overall extent of fibrosis score in a patient. The overall pattern can also be categorized by its consistency with the usual interstitial pneumonia (UIP) pattern.
Physiologic predictors
A series of physiologic variables on pulmonary function testing have been used to assess disease severity and predict survival in IPF. Those most consistently associated with prognosis of PF are forced vital capacity (FVC), total lung capacity (TLC) and diffusing capacity of the lung for carbon dioxide (DlCO). To assess all three combined, a composite physiologic index has been developed.
Pathologic predictors
Usual interstitial pneumonia (UIP) pattern is the histopathologic pattern that identifies IPF. Fibroblastic foci are hypothesized to play a key role in the pathophysiology of IPF and sometimes to predict survival.
Biomarker predictors
Biomarkers from blood and bronchoalveolar lavage (BAL) fluid have been shown to correlate with disease progression and survival in IPF. Some biomarkers include B-type natriuretic peptides, albumin levels, and Krebs von den Lungen-6 (KL-6), surfactant proteins A and D (SP-A and SP-D).
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