title: Interobserver reproducibility of the controlled attenuation parameter (CAP) for quantifying liver steatosis.
abstract: OBJECTIVE
  This study was conducted to prospectively investigate the interobserver reproducibility of controlled attenuation parameter (CAP) measurements and the relationship among the CAP and body mass index (BMI), gender and age.
  
  
  METHODS
  Consecutive subjects were studied using the M+ probe of the FibroScan device (Echosens, Paris, France). Measurements were performed by two raters (rater1 and rater2). Interobserver agreement was assessed by using the concordance correlation coefficient (CCC). The Pearson r coefficient was used to test correlation between two study variables, and linear regression was used for the multivariate model.
  
  
  RESULTS
  Three hundred fifty-one subjects (227 males and 124 females) were prospectively studied. The CCC was 0.82 (95 % CI 0.78-0.85) overall, 0.80 (95 % CI 0.75-0.85) for BMI <25 kg/m(2), 0.76 (95 % CI 0.69-0.84) for BMI 25-29 kg/m(2) and 0.65 (95 % CI 0.41-0.88) for BMI ≥30 kg/m(2). The CCC was 0.44 (95 % CI 0.31-0.56) for CAP values ≤240 dB/m and 0.72 (95 % CI 0.65-0.79) for CAP values >240 dB/m. In univariate analysis, age and BMI by gender were correlated with the CAP. Multiple regression analysis confirmed the relationship of the CAP with age and BMI, but not with gender.
  
  
  CONCLUSIONS
  The results of this study show that the interreader agreement in CAP measurement is good. In healthy volunteers, the CAP is strongly correlated with age and BMI.
authors.affiliation: Ultrasound Unit, Department of Infectious Diseases, Fondazione IRCCS Policlinico San Matteo, University of Pavia, Via Taramelli 5, 27100, Pavia, Italy. giovanna.ferraioli@unipv.it.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Ferraioli
authors.affiliation: Clinical Epidemiology and Biometric Unit, Fondazione IRCCS Policlinico San Matteo, Viale Camillo Golgi 19, 27100, Pavia, Italy.
authors.forename: Carmine
authors.initials: C
authors.lastname: Tinelli
authors.affiliation: Ultrasound Unit, Department of Infectious Diseases, Fondazione IRCCS Policlinico San Matteo, University of Pavia, Via Taramelli 5, 27100, Pavia, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Lissandrin
authors.affiliation: Ultrasound Unit, Department of Infectious Diseases, Fondazione IRCCS Policlinico San Matteo, University of Pavia, Via Taramelli 5, 27100, Pavia, Italy.
authors.forename: Mabel
authors.initials: M
authors.lastname: Zicchetti
authors.affiliation: Department of Applied Health Sciences, Istituto di Cura "Santa Margherita", University of Pavia, Via Emilia 12, 27100, Pavia, Italy.
authors.forename: Mariangela
authors.initials: M
authors.lastname: Rondanelli
authors.affiliation: Department of Internal Medicine, Fondazione IRCCS Policlinico San Matteo, Viale Camillo Golgi 19, 27100, Pavia, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Perani
authors.affiliation: Department of "Medicina Diagnostica e dei Servizi", Fondazione IRCCS Policlinico San Matteo, Viale Camillo Golgi 19, 27100, Pavia, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Bernuzzi
authors.affiliation: Department of "Medicina Diagnostica e dei Servizi", Fondazione IRCCS Policlinico San Matteo, Viale Camillo Golgi 19, 27100, Pavia, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Salvaneschi
authors.affiliation: Ultrasound Unit, Department of Infectious Diseases, Fondazione IRCCS Policlinico San Matteo, University of Pavia, Via Taramelli 5, 27100, Pavia, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Filice
keywords: Controlled attenuation parameter; Interobserver agreement; Liver steatosis; Noninvasive techniques; Reproducibility studies; Transient elastography