• Interstitial Fibrosis
• Idiopathic pulmonary fibrosis

An accurate and early diagnosis of idiopathic pulmonary fibrosis (IPF) is critically required for patients and care providers because it dictates very specific management decisions that include referral to transplant, access to new approved drugs, avoidance of immunosuppression and potential referral to palliative care.1 While the original diagnosis of IPF was highly dependent on patterns observed on histology, in 2002 the American Thoracic Society (ATS)/European Respiratory Society (ERS) guideline altered the approach to diagnosis so as to include a clinical–radiological–pathological multidisciplinary diagnosis.2 A careful history, searching for subtle evidence of connective tissue disease, exposures and other known causes for interstitial lung disease (ILD), was emphasised. A radiographic pattern of usual interstitial pneumonia (UIP) on high-resolution CT (HRCT) was described, characterised by basal-predominant fibrosis with peripheral reticular markings, traction airway change, architectural distortion and honeycombing.

With this new classification system, it was proposed, characteristic HRCT findings could lead to a confident diagnosis of IPF without the need for a biopsy. The advantage of using HRCT patterns as a surrogate for pathological findings was particularly appealing given data describing increased risk for acute exacerbation and death following lung biopsy.3 Support for such an approach was increased by studies demonstrating agreement between radiographic and pathological findings. Raghu et al4 found that the specificity of HRCT for UIP was 90%. Flaherty et al5 found that the HRCT interpretation of definite UIP in biopsy-proven UIP and non-specific interstitial pneumonia (NSIP) had 100% specificity. Hunninghake et al6 found that in a blinded prospective evaluation of patients with surgical lung biopsies, a confident HRCT diagnosis of UIP was 95% specific for the pathological finding of UIP. HRCT appearance was also predictive of survival: a definite UIP pattern on HRCT (having all the features described above) was associated with a lower survival …