TY - JOUR T1 - Variable Utility of Mosaic Attenuation to Distinguish Fibrotic Hypersensitivity Pneumonitis from Idiopathic Pulmonary Fibrosis JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.00531-2019 SP - 1900531 AU - J. Barnett AU - P.L. Molyneaux AU - B. Rawal AU - R. Abdullah AU - S.S. Hare AU - R. Vancheeswaran AU - S.R. Desai AU - T.M. Maher AU - A.U. Wells AU - A. Devaraj Y1 - 2019/01/01 UR - http://erj.ersjournals.com/content/early/2019/04/25/13993003.00531-2019.abstract N2 - Background: Mosaic attenuation on CT has been identified in international guidelines as an important diagnostic feature of fibrotic hypersensitivity pneumonitis (FHP) as opposed to idiopathic pulmonary fibrosis (IPF). However, mosaic attenuation (MA) comprises several different radiological signs (low density lobules [LDL], preserved lobules [PL], air trapping [AT] and the so-called “headcheese sign”) which may have differing diagnostic utility. Furthermore, the extent of MA required to distinguish these two diagnoses is uncertain, and thresholds of MA from international guidelines have not been validated.Methods: Inspiratory and expiratory CTs were evaluated by two readers in 102 patients (IPF n=57; FHP n=45) using a semiquantitative scoring system for MA. Findings were validated in an external cohort from a secondary referral institution (IPF n=34; FHP n=28).Results: LDL and AT were a frequent finding in IPF, present in up to 51% of patients. A requirement for increasing extent of LDL and AT based on guidelines (ATS and Fleischner Society) was associated with increased specificity for the diagnosis of FHP (0.96 and 0.98, respectively) but reduced sensitivity (0.16 and 0.20 respectively). The “headcheese” sign was found to be highly specific (0.93), and moderately sensitive (0.49) for a high confidence diagnosis of FHP. The high specificity of the headcheese sign was maintained in the validation cohort, and when patients with other CT features of FHP were excluded.Conclusion: MA is a frequent finding in IPF. However, the headcheese sign can be confidently considered as being inconsistent with a diagnosis of IPF and specific for FHP.FootnotesThis manuscript has recently been accepted for publication in the European Respiratory Journal. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article.Conflict of interest: Dr. Barnett has nothing to disclose.Conflict of interest: PLM has, via his institution, received industry-academic funding from Roche, Boehringer Ingelheim and Galapagos and has received speakers fees from Roche.Conflict of interest: Dr. Rawal has nothing to disclose.Conflict of interest: Dr. Abdullah has nothing to disclose.Conflict of interest: Dr. Hare has nothing to disclose.Conflict of interest: Dr. Vancheeswaran has nothing to disclose.Conflict of interest: Dr. Desai reports: I am co-organiser of an educational course convened by Boehringer-Ingelheim. This is a “hands-on” workshop for pulmonologists and radiologists working in the field. The aim of the course is purely educational and i) does not focus on any particular disease (and specifically not IPF or hypersensitivity pneumonitis) and ii) does not promote any specific treatment or management..Conflict of interest: TMM has, via his institution, received industry-academic funding from GlaxoSmithKline R&D and UCB and has received consultancy or speakers fees from Apellis, Astra Zeneca, aTyr Pharma, Bayer, Biogen Idec, Boehringer Ingelheim, Galapagos, GlaxoSmithKline R&D, Indalo, Pliant, ProMetic, Roche, Samumed and UCB.Conflict of interest: Dr. Wells reports personal fees from Intermune, personal fees from Boehringer Inlgeheim, personal fees from Gilead, personal fees from MSD, personal fees from Roche, personal fees from Bayer, personal fees from Chiesi, outside the submitted work.Conflict of interest: Dr. Devaraj reports personal fees from GSK, personal fees from Roche, personal fees from boehringer ingelheim, outside the submitted work. ER -