Joseph Barnett1, Philip L Molyneaux2, Bhavin Rawal3, Rezaur Abdullah4, Samanjit S Hare5, Rama Vancheeswaran4, Sujal R Desai3, Toby M Maher2, Athol U Wells6, Anand Devaraj3,2. 1. Dept of Radiology, Royal Brompton Hospital, London, UK j.barnett2@rbht.nhs.uk. 2. National Heart and Lung Institute, Imperial College London, London, UK. 3. Dept of Radiology, Royal Brompton Hospital, London, UK. 4. Dept of Respiratory Medicine, Barnet Hospital, Royal Free NHS Foundation Trust, London, UK. 5. Dept of Radiology, Barnet Hospital, Royal Free NHS Foundation Trust, Royal Free NHS Foundation Trust, London, UK. 6. Interstitial Lung Disease Unit, Royal Brompton Hospital, London, UK.
Abstract
BACKGROUND: Mosaic attenuation on computed tomography (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 comprises several different radiological signs (low-density lobules, preserved lobules, air trapping and the so-called "headcheese sign") which may have differing diagnostic utility. Furthermore, the extent of mosaic attenuation required to distinguish these two diagnoses is uncertain and thresholds of mosaic attenuation from international guidelines have not been validated. METHODS: Inspiratory and expiratory CT scans were evaluated by two readers in 102 patients (IPF n=57; FHP n=45) using a semiquantitative scoring system for mosaic attenuation. Findings were validated in an external cohort from a secondary referral institution (IPF n=34; FHP n=28). RESULTS: Low-density lobules and air trapping were a frequent finding in IPF, present in up to 51% of patients. A requirement for increasing extent of low-density lobules and air trapping based on guidelines (American Thoracic Society 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: Mosaic attenuation 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.
BACKGROUND: Mosaic attenuation on computed tomography (CT) has been identified in international guidelines as an important diagnostic feature of fibrotic hypersensitivitypneumonitis (FHP) as opposed to idiopathic pulmonary fibrosis (IPF). However, mosaic attenuation comprises several different radiological signs (low-density lobules, preserved lobules, air trapping and the so-called "headcheese sign") which may have differing diagnostic utility. Furthermore, the extent of mosaic attenuation required to distinguish these two diagnoses is uncertain and thresholds of mosaic attenuation from international guidelines have not been validated. METHODS: Inspiratory and expiratory CT scans were evaluated by two readers in 102 patients (IPF n=57; FHP n=45) using a semiquantitative scoring system for mosaic attenuation. Findings were validated in an external cohort from a secondary referral institution (IPF n=34; FHP n=28). RESULTS: Low-density lobules and air trapping were a frequent finding in IPF, present in up to 51% of patients. A requirement for increasing extent of low-density lobules and air trapping based on guidelines (American Thoracic Society 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: Mosaic attenuation 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.
Authors: Ganesh Raghu; Martine Remy-Jardin; Christopher J Ryerson; Jeffrey L Myers; Michael Kreuter; Martina Vasakova; Elena Bargagli; Jonathan H Chung; Bridget F Collins; Elisabeth Bendstrup; Hassan A Chami; Abigail T Chua; Tamera J Corte; Jean-Charles Dalphin; Sonye K Danoff; Javier Diaz-Mendoza; Abhijit Duggal; Ryoko Egashira; Thomas Ewing; Mridu Gulati; Yoshikazu Inoue; Alex R Jenkins; Kerri A Johannson; Takeshi Johkoh; Maximiliano Tamae-Kakazu; Masanori Kitaichi; Shandra L Knight; Dirk Koschel; David J Lederer; Yolanda Mageto; Lisa A Maier; Carlos Matiz; Ferran Morell; Andrew G Nicholson; Setu Patolia; Carlos A Pereira; Elisabetta A Renzoni; Margaret L Salisbury; Moises Selman; Simon L F Walsh; Wim A Wuyts; Kevin C Wilson Journal: Am J Respir Crit Care Med Date: 2020-08-01 Impact factor: 30.528
Authors: Regina Celia Carlos Tibana; Maria Raquel Soares; Karin Mueller Storrer; Gustavo de Souza Portes Meirelles; Katia Hidemi Nishiyama; Israel Missrie; Ester Nei Aparecida Martins Coletta; Rimarcs Gomes Ferreira; Carlos Alberto de Castro Pereira Journal: BMC Pulm Med Date: 2020-11-16 Impact factor: 3.317
Authors: Christopher J Ryerson; Tamera J Corte; Jeffrey L Myers; Simon L F Walsh; Sabina A Guler Journal: Eur Respir J Date: 2021-12-16 Impact factor: 16.671