title: Conversion and reliability of two urological grading systems in infants: the Society for Fetal Urology and the urinary tract dilatation classifications system.
abstract: BACKGROUND
  The urinary tract dilation (UTD) classification system was proposed in 2014.
  
  
  OBJECTIVE
  To evaluate the correspondence and reliability of two US grading systems for postnatal urinary tract dilatation in infants: the Society for Fetal Urology (SFU) and the UTD systems.
  
  
  METHODS
  We assessed 180 kidneys in infants younger than 1 year. Four radiologists assessed the kidneys twice using both the SFU system (grades 0 to 4) and the UTD system (grades normal, P1, P2, P3). The SFU system was re-categorized into SFU-A (grades 0, 1-2, 3, 4) and into SFU-B (grades 0-1, 2, 3, 4). The Cohen kappa statistic was used for estimating agreement of both UTD-SFU-A and UTD-SFU-B.
  
  
  RESULTS
  The Cohen kappa was significantly higher between UTD and SFU-B as compared to the UTD and SFU-A (0.75 vs. 0.50, P < 0.001). Intra-observer agreement was similar for the two grading systems (SFU 0.64-0.88 vs. UTD 0.48-0.92, P = 0.050-0.885). SFU grades 2 and 3 showed fair to moderate inter-observer agreement and corresponding UTD grades P1 and P2 showed moderate to substantial agreement. The overall inter-observer agreement was significantly higher for the UTD system than for the SFU system during the first assessment (95% confidence interval [CI]: right kidney, -0.069 to -0.062; left kidney, -0.048 to -0.043).
  
  
  CONCLUSIONS
  Correspondence between the systems was poor using a recommended re-categorization (SFU-A). An alternative re-categorization (SFU-B) was found to be more appropriate for establishing correspondence between the systems. Both systems were reliable, with good intra- and inter-observer agreement for the assessment of infant kidneys, but the UTD system had better inter-observer agreement.
authors.affiliation: Department of Radiology, Ajou University School of Medicine, Ajou University Medical Center, 164 World cup-ro, Yeongtong-gu, Suwon, Korea, 443-380.
authors.forename: Miran
authors.initials: M
authors.lastname: Han
authors.affiliation: Department of Radiology, Ajou University School of Medicine, Ajou University Medical Center, 164 World cup-ro, Yeongtong-gu, Suwon, Korea, 443-380. catharina315@aumc.ac.kr.
authors.forename: Hyun Gi
authors.identifier: http://orcid.org/0000-0002-0086-543X
authors.initials: HG
authors.lastname: Kim
authors.affiliation: Office of Biostatistics, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Jung-Dong
authors.initials: JD
authors.lastname: Lee
authors.affiliation: Department of Radiology, Ajou University School of Medicine, Ajou University Medical Center, 164 World cup-ro, Yeongtong-gu, Suwon, Korea, 443-380.
authors.forename: Seon Young
authors.initials: SY
authors.lastname: Park
authors.affiliation: Department of Radiology, Ajou University School of Medicine, Ajou University Medical Center, 164 World cup-ro, Yeongtong-gu, Suwon, Korea, 443-380.
authors.forename: Young Keun
authors.initials: YK
authors.lastname: Sur
mesh_terms: D004108:Dilatation, Pathologic / Q000145:classification / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000145:classification* / Q000000981:diagnostic imaging*; D007223:Infant; D007668:Kidney / Q000002:abnormalities / Q000000981:diagnostic imaging; D008297:Male; D015203:Reproducibility of Results; D012189:Retrospective Studies
keywords: Infants; Postnatal hydronephrosis; Reliability; Society for Fetal Urology classification system; Ultrasound; Urinary tract dilatation classification system