Integrating Clinical Probability into the Diagnostic Approach to Idiopathic Pulmonary Fibrosis: An International Working Group Perspective

Background. When considering the diagnosis of idiopathic pulmonary fibrosis (IPF), experienced \r\nclinicians integrate clinical features that help to differentiate IPF from other fibrosing interstitial lung \r\ndiseases, thus generating a “pre-test” probability of IPF. The aim of this international working group \r\nperspective was to summarize these features using a tabulated approach similar to chest HRCT and \r\nhistopathologic patterns reported in the international guidelines for the diagnosis of IPF, and to help \r\nformally incorporate these clinical likelihoods into diagnostic reasoning to facilitate the diagnosis of \r\nIPF.\r\nMethods. The committee group identified factors that influence the clinical likelihood of a diagnosis \r\nof IPF, which was categorized as a pre-test clinical probability of IPF into “high” (70-100%), \r\n“intermediate” (30-70%), or “low” (0-30%). After integration of radiological and histopathological \r\nfeatures, the post-test probability of diagnosis was categorized into “definite” (90-100%), “high \r\nconfidence” (70-89%), “low confidence” (51-69%), or “low” (0-50%) probability of IPF. \r\nFindings. A conceptual Bayesian framework was created, integrating the clinical likelihood of IPF \r\n(“pre-test probability of IPF”) with the HRCT pattern, the histopathology pattern when available, \r\nand/or the pattern of observed disease behavior into a “post-test probability of IPF”. The diagnostic \r\nprobability of IPF was expressed using an adapted diagnostic ontology for fibrotic interstitial lung \r\ndiseases.\r\nInterpretation. The present approach will help incorporate the clinical judgement into the diagnosis \r\nof IPF, thus facilitating the application of IPF diagnostic guidelines and, ultimately improving \r\ndiagnostic confidence and reducing the need for invasive diagnostic techniques.