title: ARFI cut-off values and significance of standard deviation for liver fibrosis staging in patients with chronic liver disease.
abstract: BACKGROUND
  Acoustic radiation force impulse (ARFI) elastometry quantifies hepatic stiffness, and thus degree of fibrosis, non-invasively. Our aim was to analyse the diagnostic accuracy of ARFI cut-off values, and the significance of a defined limit of standard deviation (SD) as a potential quality parameter for liver fibrosis staging in patients with chronic liver diseases (CLD).
  
  
  METHODS
  153 patients with CLD (various aetiologies) undergoing liver biopsy, and an additional 25 patients with known liver cirrhosis, were investigated. ARFI measurements were performed in the right hepatic lobe, and correlated with the histopathological Ludwig fibrosis score (inclusion criteria: at least 6 portal tracts). The diagnostic accuracy of cut-off values was analysed with respect to an SD limit of 30% of the mean ARFI value.
  
  
  RESULTS
  The mean ARFI elastometry showed 1.95 ± 0.87 m/s (range 0.79-4.40) in 178 patients (80 female, 98 male, mean age: 52 years). The cut-offs were 1.25 m/s for F ≥ 2, 1.72 m/s for F ≥ 3 and 1.75 m/s for F = 4, and the corresponding AUROC 80.7%, 86.2% and 88.7%, respectively. Exclusion of 31 patients (17.4%) with an SD higher than 30% of the mean ARFI improved the diagnostic accuracy: The AUROC for F ≥ 2, F ≥ 3 and F = 4 were 86.1%, 91.2% and 91.5%, respectively.
  
  
  CONCLUSIONS
  The diagnostic accuracy of ARFI can be improved by applying a maximum SD of 30% of the mean ARFI as a quality parameter--which however leads to an exclusion of a relevant number of patients. ARFI results with a high SD should be interpreted with caution.
authors.affiliation: Department of Internal Medicine 1, University of Erlangen, Ulmenweg 18, 91054 Erlangen, Germany.
authors.forename: Ruediger S
authors.initials: RS
authors.lastname: Goertz
authors.forename: Joerg
authors.initials: J
authors.lastname: Sturm
authors.forename: Lukas
authors.initials: L
authors.lastname: Pfeifer
authors.forename: Dane
authors.initials: D
authors.lastname: Wildner
authors.forename: David L
authors.initials: DL
authors.lastname: Wachter
authors.forename: Markus F
authors.initials: MF
authors.lastname: Neurath
authors.forename: Deike
authors.initials: D
authors.lastname: Strobel
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001706:Biopsy; D002908:Chronic Disease; D054459:Elasticity Imaging Techniques; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology*; D008103:Liver Cirrhosis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012720:Severity of Illness Index; D055815:Young Adult