Variability in assessing for BK viremia: whole blood is not reliable and plasma is not above reproach - a retrospective analysis.

Polyomavirus nephropathy (PVN) is a major complication of kidney transplantation. Most reports describe polyomavirus viremia either precedes or is detectable at the time of diagnosis of PVN. This association is the basis of current screening recommendations. We retrospectively reviewed the PCR results of blood and urine samples from 29 kidney transplant recipients with biopsy-proven PVN. Biopsies were performed for a rise in serum creatinine or persistent high-level BK viruria. All biopsies showed polyoma virus large T-antigen expression in tubular epithelium using immunohistochemistry. All had viruria preceding or at the time of biopsy (range, 5.2 × 104 to >25 × 106 BKV DNA copies/ml). Twenty (69%) had viremia ranging from 2.5 × 103 to 4.3 × 106 copies/ml at the time of the biopsy. Via blood BK PCR assay, nine (31%) had no BK viremia detected either preceding or at the time of the biopsy. In five recipients where sufficient specimen permitted, additional plasma BK assessment revealed positive detection of viremia. A comparative analysis of assays from two centres was performed with spiked samples. BK DNA may not be detected in the blood of some kidney transplant recipients with histologically confirmed PVN. This may reflect limitation of whole blood as opposed to plasma-based BK DNA assessment.

Agrawal N ，Echenique IA ，Meehan SM ，Limaye AP ，Cook L ，Chang A ，Harland RC ，Javaid B ，Kadambi PV ，Matushek S ，Williams J ，Josephson MA ... -  《-》

BIOPSY-PROVEN BK VIRUS NEPHROPATHY WITHOUT DETECTABLE BK VIREMIA IN A ONE-YEAR POST-KIDNEY TRANSPLANT RECIPIENT.

Ruangkanchanasetr P ，Pumchandh N ，Satirapoj B ，Termmathurapoj S ，Pongthanapisith V ... -  《SOUTHEAST ASIAN JOURNAL OF TROPICAL MEDICINE AND PUBLIC HEALTH》

The status of BK polyomavirus replication in adult renal transplant recipients in northeastern Poland.

BK polyomavirus (BKV) infection and BKV-associated nephropathy (BKVAN) are among the most important problems in renal transplantation. We aimed to determine the incidence of BK viruria, viremia, and BKVAN in renal transplant recipients in the northeastern part of Poland. Urine and blood samples from 126 cadaveric renal transplant recipients were analyzed for BK viruria and viremia using quantitative real-time polymerase chain reaction and the patients were followed prospectively. The diagnosis of BKVAN was established on the allograft biopsy. Based on the BKV DNA analysis, the patients were divided into three groups: group 1 (n=89; 70.6%) without viruria or viremia, group 2 (n=24; 19.1%) with isolated viruria, and group 3 (n=13; 10.3%) with both viruria and viremia. The presence of BK viremia negatively correlated with time after the transplantation. BK viruria was associated with mycophenolate mofetil daily dose. In group 3 there were four patients (3.2%) with high viremia (>10(4) genome equivalents [gEq]/mL) and viruria (>10(7) gEq/mL) loads. Only one patient from this group developed clinical symptoms and had BKVAN in allograft biopsy. In all four cases, the maintenance immunosuppression therapy was based on tacrolimus and steroids. Prevalence of BKV infection in renal transplant recipients in the northeastern part of Poland is similar to that reported by studies from other countries. We confirm that BK viremia could be predicted by the presence of intense viruria. Time after transplantation and the type of immunosuppression strategy are the most important predictors of BK viremia and viruria in patients after renal transplantation.

Naumnik B ，Kowalewska J ，Zalewski G ，Charkiewicz R ，Myśliwiec M ... -  《-》

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 ... -  《-》

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 ... -  《-》