title: Correlation between urine and serum BK virus levels after renal transplantation.
abstract: BACKGROUND
  Quantification of the serum level of BK virus is used as a surrogate marker for the early onset of BK virus nephropathy. However, little is known about the diagnostic value of the urine level of BK virus for nephropathy or the relationship between the serum and urine viral load. We investigated the correlation between urine and serum BK virus levels after renal transplantation.
  
  
  METHODS
  From November 2008 to August 2013, a total of 270 renal transplant patients who were followed at our institution were included in this study. Urine and serum were collected simultaneously. BK virus levels were quantified in 894 urine and serum samples using a real-time polymerase chain reaction assay.
  
  
  RESULTS
  BK virus was detected in 178 urine samples and 36 serum samples. Among the BK virus-positive urine subjects, the positive predictive value for viral detection in the serum was 9% (13/147) when the urinary virus level was <10(7) copies/mL and 74% (23/31) when the urinary virus was ≥ 10(7) copies/mL. Serum BK viral levels were ∼2-3 log units lower than those in urine.
  
  
  CONCLUSIONS
  BK virus was detected more frequently in serum when present in urine at ≥ 10(7) copies/mL after renal transplantation.
authors.affiliation: Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: yfunahashi@med.nagoya-u.ac.jp.
authors.forename: Y
authors.initials: Y
authors.lastname: Funahashi
authors.affiliation: Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kato
authors.affiliation: Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Fujita
authors.affiliation: Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tsuruta
authors.affiliation: Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Inoue
authors.affiliation: Department of Urology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Gotoh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001739:BK Virus / Q000235:genetics / Q000302:isolation & purification*; D002648:Child; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D006801:Humans; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D027601:Polyomavirus Infections / Q000097:blood / Q000652:urine / Q000821:virology*; D055815:Young Adult
chemical_list: D004279:DNA, Viral