title: Analytical and clinical performance characteristics of the Simplexa BK virus quantitative PCR assay for the diagnosis of polyomavirus-associated nephropathy in renal transplant recipients using plasma and urine specimens.
abstract: BACKGROUND
  Polyomavirus-associated nephropathy is a significant cause of kidney rejection in renal transplant recipients. Quantification of BK viral load in plasma and urine can predict the development of polyomavirus-associated nephropathy, though each assay requires careful evaluation of analytical and clinical performance characteristics for optimal use.
  
  
  OBJECTIVE
  This study evaluated the analytical and clinical performance characteristics of the Simplexa BK virus quantitative PCR assay.
  
  
  METHODS
  Analytical validation was performed using commercial standards, BK virus stock culture, and patient specimens. Clinical performance was evaluated using biopsy-proven BK nephropathy as the gold standard.
  
  
  RESULTS
  The Simplexa BK virus quantitative PCR assay was linear over a range of 2.7-10.4 log(10) copies/mL. Limit of detection was 2.7-2.8 log(10) copies/mL in plasma and urine samples. Sensitivities were 100% and 100% and specificities were 84% and 86% for plasma and urine samples, respectively, when compared to a reference BK assay. Clinical cutoff values of 4.0 log(10) copies/mL (plasma) and 7.5 log(10) copies/mL (urine) yielded 100% sensitivity and specificities of 87.5% and 85%, respectively, for biopsy-proven polyomavirus nephropathy.
  
  
  CONCLUSIONS
  The Simplexa BK virus quantitative PCR assay has high sensitivity and acceptable analytical characteristics for clinical use. The clinical cutoff values presented here provide a rational approach to the monitoring and treatment of renal transplant recipients for polyomavirus-associated nephropathy.
authors.affiliation: Department of Laboratory Medicine, Clinical Laboratories, University of California San Francisco, San Francisco, CA 94107, United States. Steve.Miller@ucsfmedctr.org
authors.forename: Steve
authors.initials: S
authors.lastname: Miller
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Liverman
authors.forename: Linda
authors.initials: L
authors.lastname: Post
authors.forename: Yasmeen
authors.initials: Y
authors.lastname: Khan
authors.forename: Carolyn
authors.initials: C
authors.lastname: Wright
mesh_terms: D001739:BK Virus / Q000302:isolation & purification*; D006801:Humans; D007674:Kidney Diseases / Q000175:diagnosis* / Q000821:virology; D016030:Kidney Transplantation; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D010949:Plasma / Q000821:virology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D027601:Polyomavirus Infections / Q000175:diagnosis* / Q000821:virology; D012680:Sensitivity and Specificity; D014180:Transplantation; D014556:Urine / Q000821:virology*; D014773:Virology / Q000379:methods