Systematic screening of BK virus by real-time PCR prevents BK virus associated nephropathy in renal transplant recipients.

BK virus associated nephropathy occurs in approximately 5% of renal transplant recipients. Quantitation of BKV DNA in serum/plasma early in the course of disease has been suggested to be an important diagnostic tool for polymavirus-associated nephropathy (PVAN). The aim of this study was to develop a BKV real-time PCR (qPCR), which could be included in a diagnostic qPCR platform. Additionally, the significance of the assay as a surrogate marker for PVAN was investigated. Quantitation of BKV DNA by qPCR was carried out on 234 serum samples from a retrospective study including 31 renal transplant recipients monitored for at least 6 months post-transplantation. BKV viremia was detected in 9 out of 31 patients. Four patients had a viral load of >10,000 copies/ml at least on one occasion. In two of these patients, PVAN was diagnosed clinically during the study period. In retrospect, these patients were shown to be BKV positive before the clinical diagnosis of PVAN was made. Another two patients had a permanent graft dysfunction, but were never clinically diagnosed with PVAN. None of the remaining five patients with BKV DNA (<10,000 copies/ml) had renal impairment. Based on these results, an algorithm was introduced at the study center in 2006 and to date, August 2011, no cases of PVAN with loss of graft have been observed. The concept of including different PCR protocols in a common qPCR platform allows laboratories with small sample numbers to perform regularly a variety of assays at a reasonable cost.

Hammarin AL ，Öqvist B ，Wahlgren J ，Falk KI ... -  《-》

Polyomavirus polymerase chain reaction as a surrogate marker of polyomavirus-associated nephropathy.

Viscount HB ，Eid AJ ，Espy MJ ，Griffin MD ，Thomsen KM ，Harmsen WS ，Razonable RR ，Smith TF ... -  《TRANSPLANTATION》

Prevalence and risk factors of polyomavirus BK replication in simultaneous pancreas/kidney transplant recipients from a single transplant center.

BK virus (BKV) replication is considered as a marker of risk for polyomavirus BK-associated nephropathy (PVAN). We evaluated the occurrence and risk factors for BKV DNA positivity following simultaneous pancreas/kidney transplantation (SPK). Point prevalence of BK viruria and viremia was assessed in 183 SPK recipients. Real-time polymerase chain reaction was used with a detection threshold of 10(3) copies/mL. High-level BKV positivity was defined as viruria and/or viremia >10(7) and >10(4) copies/mL, respectively. BKV-positive patients were retested after 4-13 months and underwent an additional six-month clinical follow-up. Urine and serum BKV positivity was detected in 28 (17.3% of available samples) and 7 (3.8%) patients, with high-level viruria and viremia occurring in 6 (3.7%) and 3 (1.6%) patients, respectively. PVAN was biopsy-confirmed in 1 and suspected as a cause of progressive renal failure in another SPK recipient. Patients with single low-level viruria did not progress to high-level positivity or PVAN at follow-up. In multivariate analysis, pre-transplant diabetes duration and delayed graft function were independently associated with BKV positivity. Point prevalence of high-level BKV positivity and PVAN was low in SPK recipients from a single center. Diabetes duration and delayed graft function were independent risk factors for BKV replication.

Mindlova M ，Boucek P ，Saudek F ，Skibova J ，Jedinakova T ，Lipar K ，Adamec M ，Hirsch HH ... -  《-》

Screening for polyomavirus associated nephropathy in renal transplantation with blood viral load measurement.

Boudreault AA ，Courtemanche C ，Latulippe E ，Côté I ，Houde I ，Deschênes L ... -  《-》

Currently recommended BK virus (BKV) plasma viral load cutoff of ≥4 log10/mL underestimates the diagnosis of BKV-associated nephropathy: a single transplant center experience.

BK virus (BKV)-associated nephropathy (BKVAN) is a major cause of renal dysfunction and graft loss in renal transplant recipients. Monitoring plasma BK viral load (BKVL) is the recommended screening tool to predict BKVAN. American Society of Transplantation (AST) guidelines define a BKVL of ≥4 log10/mL (10,000 copies) as presumptive BKVAN and recommend reduction in immunosuppression. We evaluated the clinical sensitivity of the quantitative BKV DNA assay in predicting risk for BKVAN using the AST-recommended BKVL cutoff. In a retrospective, single-center study, all patients who underwent renal transplant at Henry Ford Hospital from January 2008 to August 2011 were analyzed (n = 490). Plasma BKVL Assay A (commercial large T antigen-based polymerase chain reaction [PCR]) was done in all patients. Renal biopsy was done if there was a rise in serum creatinine ≥0.5 mg from baseline. BKVAN was confirmed by biopsy. As a subset to this study, from the same cohort, data for a set of 20 consecutive Assays A and B (in-house VP1-based PCR assay) from 15 patients over a period of 3 months were collected. Differences in physicians' clinical decision-making (CDM) were analyzed between the 2 assays using chi-square test. A total of 413 patients met the inclusion criteria, of which 222 patients had BK viremia. Among the 248 patients who had a renal biopsy done, 31 (12.5%) were found to have BKVAN. Eleven of the 31 (35%) patients had BKVL consistently <4 log10/mL, and thus were not diagnosed to have BKVAN using the AST-recommended BKVL cutoff of ≥4 log10/mL. A total of 8 patients lost their graft owing to BKVAN, including 3 patients with BKVL <4 log10/mL. Using a cutoff point of plasma BKVL of ≥4 log10/mL, the sensitivity, specificity, positive predictive value, and negative predicative value of the PCR Assay A for the diagnosis of biopsy-proven BKVAN were 64.5%, 98.4%, 87.0%, and 94.5%, respectively, and for the diagnosis of presumptive nephropathy were found to be 76.6%, 99.4%, 95.8%, and 96.4%, respectively. In the second part of the study, presumptive nephropathy was detected in 8 samples using Assay A and 14 samples using Assay B. Six samples in Assay A would have led to no changes in the CDM in terms of reduction in immunosuppression. Kidney biopsy was carried out in 5 patients, 4 of whom had BKVAN and had Assay B log count of ≥5. If Assay A had been used in CDM, BKVAN would have been missed in 1 patient. Utilizing the current AST guideline cutoff of ≥4 log10 /mL, the PCR Assay A underestimated the diagnosis of BKVAN. Urgent standardization of the various BKVL assays and establishment of universal cutoff points is imperative to avoid BKVAN-related graft loss.

Hassan S ，Mittal C ，Amer S ，Khalid F ，Patel A ，Delbusto R ，Samuel L ，Alangaden G ，Ramesh M ... -  《-》