Idiopathic pulmonary fibrosis (IPF) is a disease where the fine, delicate structure of the lungs is replace by a hard, concrete-like substance called fibrous matrix. This prevents the normal functions of the lung, such as the transfer of oxygen from the air to the body, it also leads to irritation and persistent cough. The speed at which this concrete-like matrix is deposited in the lung varies between different people, but ultimately leads to death. Unfortunately it is difficult to predict who will get worse quickly, and who will get worse slowly. Furthermore, there are no treatments that can improve the outlook for people with IPF at the current time. The aim of this study is to develop a biological test that can predict which people with IPF are going to have slowly progressive disease compared with rapidly progressive disease. More importantly these biological tests will hopefully be able to be used to show whether a current, or new treatment, is working in an individual patient. This information will help patients plan their future when the receive a diagnosis of IPF and will help in the development of new treatments for this condition, which are so urgently sought.