Pulmonary fibrosis (PF) is a condition in which the lung’s integrity becomes impaired over time, preventing the optimal respiratory flow of air into the lungs and lessening the transport of oxygen into the bloodstream and to other organs.
The cells’ access to oxygen becomes scarce, which is detrimental to the organism and increases the risk of cellular stress and cellular death in different locations of the body.
What are biomarkers?
Biomarkers are indicators of change in our cells and organs. When the organs of a PF patient suffer from stress like oxygen privation, red flags are raised that allow physicians to detect the extent of damage the condition is causing each individual. This assessment helps establish an individual prognosis.
Unfortunately, individual risk of mortality in pulmonary fibrosis patients is difficult to evaluate due to the lack of reliable prediction models. The use of biomarkers in prognosis remains experimental and is not widely used in clinical practice.
Typical biomarkers in PF
Biomarkers present in the blood and bronchoalveolar lavage (BAL) fluid of patients with idiopathic pulmonary fibrosis (IPF) have been shown to correlate with disease progression and survival.
Here is a list of biomarkers, still at an experimental phase, to help with prognosis in IPF patients:
- B-type natriuretic peptide (BNP) is a hormone that is produced in the heart and released in response to changes in pressure inside the heart;
- Albumin protein levels negatively correlate with prognosis in many diseases and predict survival in patients with idiopathic interstitial pneumonias awaiting transplantation;
- Krebs von den Lungen-6 (KL-6) is a protein and a sensitive marker for interstitial lung diseases; patients with IPF and higher KL-6 levels may have reduced survival;
- Surfactant proteins A and D (SP-A and SP-D) are secreted in the lungs and increased levels in the blood are associated with breakdown of the alveoli;
- Matrix metalloproteinases (MMPs) appear to be elevated in both blood and BAL fluid in patients with IPF;
- CC-chemokines (CCLs) that play a role in the migration of cells of the immune system are elevated in cases of IPF. CCL-18 is produced by macrophages (first-defense immune cells) in the lungs, and in the blood is a strong predictor of mortality. Elevated CCL-2, -17, and -22 in BAL fluid may predict poor outcome;
- Fibrocytes are cells involved in tissue repair. Circulating levels in the blood are elevated in cases of IPF and increase further during acute exacerbations. They appear to be a predictor of early mortality;
- Count of neutrophil cells (one type of white blood cells involved in responding to microbial infection) in BAL fluid may be useful in predicting mortality.