title: Multiparametric MRI of the prostate: diagnostic performance and interreader agreement of two scoring systems.
abstract: OBJECTIVE
  To compare the diagnostic accuracies and interreader agreements of the Prostate Imaging Reporting and Data System (PI-RADS) v. 2 and University of California San Francisco (UCSF) multiparametric prostate MRI scale for diagnosing clinically significant prostate cancer.
  
  
  METHODS
  This institutional review board-approved retrospective study included 49 males who had 1.5 T endorectal MRI and prostatectomy. Two radiologists scored suspicious lesions on MRI using PI-RADS v. 2 and the UCSF scale. Percent agreement, 2 × 2 tables and the area under the receiver operating characteristic curves (Az) were used to assess and compare the individual and overall scores of these scales. Interreader agreements were estimated with kappa statistics.
  
  
  RESULTS
  Reader 1 (R1) detected 78 lesions, and Reader 2 (R2) detected 80 lesions. Both identified 52 of 65 significant cancers. The Az for PI-RADS v. 2 and UCSF scale for R1 were 0.68 and 0.69 [T2 weighted imaging (T2WI)], 0.75 and 0.68 [diffusion-weighted imaging (DWI)] and 0.64 and 0.72 (overall score), respectively, and were 0.72 and 0.75 (T2WI), 0.73 and 0.67 (DWI) and 0.66 and 0.75 (overall score) for R2. The dynamic contrast-enhanced percent agreements between scales were 100% (R1) and 95% (R2). PI-RADS v. 2 DWI of R1 performed better than UCSF DWI (Az = 0.75 vs Az = 0.68; p = 0.05); no other differences were found. The interreader agreements were higher for PI-RADS v. 2 (T2WI: 0.56 vs 0.42; DWI: 0.60 vs 0.46; overall: 0.61 vs 0.42). The UCSF approach to derive the overall PI-RADS v. 2 scores increased the Az for the identification of significant cancer (R1 to 0.76, p < 0.05; R2 to 0.71, p = 0.35).
  
  
  CONCLUSIONS
  Although PI-RADS v. 2 DWI score may have a higher discriminatory performance than the UCSF scale counterpart to diagnose clinically significant cancer, the utilization of the UCSF scale weighing system for the integration of PI-RADS v. 2 individual parameter scores improved the accuracy its overall score.
  
  
  CONCLUSIONS
  PI-RADS v. 2 is moderately accurate for the identification of clinically significant prostate cancer, but the utilization of alternative approaches to derive the overall PI-RADS v. 2 score, including the one used by the UCSF system, may improve its diagnostic accuracy.
authors.affiliation: 1 Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.|2 Department of Radiology, School of Medicine, China Medical University, Tai Chung City, Central Taiwan, Taiwan.
authors.forename: Wei-Ching
authors.initials: WC
authors.lastname: Lin
authors.affiliation: 3 Division of Radiology, Department of Internal Medicine, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Valdair F
authors.initials: VF
authors.lastname: Muglia
authors.affiliation: 4 Department of Pathology, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Gyl E B
authors.initials: GE
authors.lastname: Silva
authors.affiliation: 3 Division of Radiology, Department of Internal Medicine, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Salomão
authors.initials: S
authors.lastname: Chodraui Filho
authors.affiliation: 5 Division of Urology, Department of Surgery and Anatomy, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Rodolfo B
authors.initials: RB
authors.lastname: Reis
authors.affiliation: 6 Departments of Radiology and Biomedical Imaging, and Urology, University of California, San Francisco, CA, USA.
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Westphalen
mesh_terms: D000368:Aged; D000465:Algorithms; D006801:Humans; D007089:Image Enhancement / Q000379:methods / Q000592:standards*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods / Q000592:standards*; D038622:Internationality; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000592:standards*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods / Q000592:standards*; D015588:Observer Variation; D017410:Practice Guidelines as Topic; D011467:Prostate / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity