title: Accuracy of MR imaging-estimated proton density fat fraction for classification of dichotomized histologic steatosis grades in nonalcoholic fatty liver disease.
abstract: OBJECTIVE
  To evaluate the diagnostic performance of previously proposed high-specificity magnetic resonance (MR) imaging-estimated proton density fat fraction (PDFF) thresholds for diagnosis of steatosis grade 1 or higher (PDFF threshold of 6.4%), grade 2 or higher (PDFF threshold of 17.4%), and grade 3 (PDFF threshold of 22.1%) by using histologic findings as a reference in an independent cohort of adults known to have or suspected of having nonalcoholic fatty liver disease (NAFLD).
  
  
  METHODS
  This prospective, cross-sectional, institutional review board-approved, HIPAA-compliant single-center study was conducted in an independent cohort of 89 adults known to have or suspected of having NAFLD who underwent contemporaneous liver biopsy. MR imaging PDFF was estimated at 3 T by using magnitude-based low-flip-angle multiecho gradient-recalled-echo imaging with T2* correction and multipeak modeling. Steatosis was graded histologically (grades 0, 1, 2, and 3, according to the Nonalcoholic Steatohepatitis Clinical Research Network scoring system). Sensitivity, specificity, and binomial confidence intervals were calculated for the proposed MR imaging PDFF thresholds.
  
  
  RESULTS
  The proposed MR imaging PDFF threshold of 6.4% to diagnose grade 1 or higher steatosis had 86% sensitivity (71 of 83 patients; 95% confidence interval [CI]: 76, 92) and 83% specificity (five of six patients; 95% CI: 36, 100). The threshold of 17.4% to diagnose grade 2 or higher steatosis had 64% sensitivity (28 of 44 patients; 95% CI: 48, 78) and 96% specificity (43 of 45 patients; 95% CI: 85, 100). The threshold of 22.1% to diagnose grade 3 steatosis had 71% sensitivity (10 of 14 patients; 95% CI: 42, 92) and 92% specificity (69 of 75 patients; 95% CI: 83, 97).
  
  
  CONCLUSIONS
  In an independent cohort of adults known to have or suspected of having NAFLD, the previously proposed MR imaging PDFF thresholds provided moderate to high sensitivity and high specificity for diagnosis of grade 1 or higher, grade 2 or higher, and grade 3 steatosis. Prospective multicenter studies are now needed to further validate these high-specificity thresholds.
authors.affiliation: From the Liver Imaging Group, Department of Radiology (A.T., A.D., G.H., J.L., L.C., J.H., T.C., M.S.M., C.B.S.), Computational and Applied Statistics Laboratory, San Diego Supercomputer Center (T.W., A.G.), Department of Pathology (M.P.), and Department of Medicine, Division of Gastroenterology (B.D.A., R.L.), University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.
authors.forename: An
authors.initials: A
authors.lastname: Tang
authors.forename: Ajinkya
authors.initials: A
authors.lastname: Desai
authors.forename: Gavin
authors.initials: G
authors.lastname: Hamilton
authors.forename: Tanya
authors.initials: T
authors.lastname: Wolfson
authors.forename: Anthony
authors.initials: A
authors.lastname: Gamst
authors.forename: Jessica
authors.initials: J
authors.lastname: Lam
authors.forename: Lisa
authors.initials: L
authors.lastname: Clark
authors.forename: Jonathan
authors.initials: J
authors.lastname: Hooker
authors.forename: Tanya
authors.initials: T
authors.lastname: Chavez
authors.forename: Brandon D
authors.initials: BD
authors.lastname: Ang
authors.forename: Michael S
authors.initials: MS
authors.lastname: Middleton
authors.forename: Michael
authors.initials: M
authors.lastname: Peterson
authors.forename: Rohit
authors.initials: R
authors.lastname: Loomba
authors.forename: Claude B
authors.initials: CB
authors.lastname: Sirlin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005234:Fatty Liver / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease / Q000145:classification* / Q000473:pathology*; D011446:Prospective Studies; D011522:Protons; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D011522:Protons