A method of prognosing or of aiding prognosis of idiopathic pulmonary fibrosis (IPF) in a patient comprises measuring in a biological sample obtained from the patient the expression of a combination of three or more genes, or expression of a combination of three or more proteins encoded by the combination of three or more genes. The three or more genes are selected from COMP, MMP3, YKL-40, CXCL13, SAA4 (constitutive SAA) and SPP1 (OPN). An elevated expression level of the combination of three or more genes, or an elevated expression level of the combination of three or more proteins, is indicative of a prognosis for shortened survival compared to median survival and a reduced expression level of the combination of three or more genes, or a reduced expression level of the combination of three or more proteins, is indicative of a prognosis for increased survival compared to median survival.
