title: Early disappearance of urinary decoy cells in successfully treated polyomavirus BK nephropathy.
abstract: BACKGROUND
  Polyomavirus BK nephropathy (BKVN) is an important infectious complication in kidney transplant patients. Regular screening using polymerase chain reaction for BK virus DNA in plasma and urinary cytology is effective for early diagnosis of BKVN. However, methods of follow-up and therapeutic targets are not well described.
  
  
  METHODS
  Ten patients with BKVN who received biweekly urinary cytology and repeat biopsies after diagnosis were retrospectively studied. Histological remission of BKVN was determined when biopsy revealed negative SV40 large T-antigen (TAg) staining. Results of urinary cytology and repeat biopsy findings were compared.
  
  
  RESULTS
  Urinary decoy cells disappeared in 8 of 10 patients 55 ± 25 (range 13-79) days after index biopsies. In those cases, allograft function was preserved and the final serum creatinine level was 2.14 ± 1.19 (0.80-4.55) mg/dL after 962 ± 393 (325-1563) days of follow-up. Two cases with persistent urinary decoy cells shedding lost their graft 195 and 362 days later. Amongst 29 repeat biopsies, there were 13 TAg-positive and 16 negative biopsies. In 12 of 13 TAg-positive biopsies (92%), urinary decoy cells were still positive, whereas at the same time in 15 TAg-negative biopsies, decoy cells had already disappeared (94%).
  
  
  CONCLUSIONS
  Cytology testing is advantageous because of its cost effectiveness. Clearance of decoy cells from urine was closely related to histological remission of BKVN, and may possibly be a therapeutic target in BKVN.
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Matsukuma
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Masutani
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Tsuchimoto
authors.affiliation: Department of Surgery and Oncology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Okabe
authors.affiliation: Department of Surgery and Oncology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kitada
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Noguchi
authors.affiliation: Department of Surgery and Oncology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; Department of Integrated Therapy for Chronic Kidney Disease, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. Electronic address: tsuruya@intmed2.med.kyushu-u.ac.jp.
authors.forename: K
authors.initials: K
authors.lastname: Tsuruya
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kitazono
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001739:BK Virus / Q000502:physiology*; D005260:Female; D006801:Humans; D007674:Kidney Diseases / Q000821:virology*; D008297:Male; D008875:Middle Aged; D014556:Urine / Q000821:virology*; D055815:Young Adult