OVERVIEW OF IPF AND EVIDENCE-BASED GUIDELINES of patients with a radiographic and histopathologic pattern of usual interstitial pneumonia (UIP) and no other identifiable cause for their ILD. 14 In addition, differing methodologies and heterogeneous study designs that are used to determine the incidence and prevalence across populations make accurate epidemiologic estimates challenging. A retrospective study of a Medicare population between 2001 and 2011 found that while the incidence of IPF in this population remained steady at a rate of 93.7 cases per 100,000 per year, the prevalence increased sharply, from 202.2 in 2001 to 495.5 in 2011. One reason, the authors suggested, could be increased survival time and earlier diagnosis. The annual increase was higher in older individuals, males, and Hispanic individuals. 15 Conversely, an analysis of claims from US adults aged 18 to 64 years showed that the incidence of IPF decreased from 2004 to 2010, with the reduction occurring primarily in younger patients. The authors suggest that this may be due to more accurate diagnosis of IPF, especially in younger adults aged 18 to 44 years. 16 Although early onset of IPF is possible in rare cases, the majority of patients in this age group with a diagnosis of IPF would more likely have other conditions such as autoimmune diseases and chronic hypersensitivity pneumonitis, which could mimic the radiographic and histologic pattern of IPF. This issue has been addressed by the expert societies, and now, according to new ATS/ERS guidelines, the exclusion of other causes of ILD, such as autoimmune conditions and chronic hypersensitivity pneumonitis, is required as a part of diagnostic work-up. 1, 8, 9