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IPF is a progressive fibrotic lung disease with a median survival of 3–5 years post-diagnosis. Fifty cases are diagnosed per 100 000 people in the UK. The incidence has been rising over the last two decades, with no cure at present. Furthermore, considerable heterogeneity exists within the disease course, making management and prognostication challenging. Kraven et al (DOI: 10.1136/thoraxjnl-2021–218563) have identified 3 IPF endotypes, termed clusters, that exhibit statistically significant differences in the GAP index (gender-age-physiology index), mortality and gas transfer (DLCO). 220 patients were identified from three pooled, publicly available blood transcriptomic datasets found on the Gene Expression Omnibus, where intermittently, data such as force vital capacity (FVC) was missing. Cluster one heavily displayed genes correlating to electron transport, cellular respiration and TGFβ. Cluster two demonstrated genes related to DNA repair, cell cycle, and apoptosis. Cluster three expressed genes corresponding to immune responses. Cluster 2 patients had the most favourable outcomes, achieving higher DLCO values, and lower GAP scores. Cluster one had the highest GAP score. Cluster three had the poorest prognosis, being 3.59 times more likely to die than patients in cluster 2. Following this discovery phase, the authors created a validated …