Polyomavirus-associated nephropathy (PVAN) is an emerging cause of kidney transplant failure affecting 1-10% of patients. As uncertainty exists regarding risk factors, diagnosis, and intervention, an independent panel of experts reviewed the currently available evidence and prepared this report. Most cases of PVAN are elicited by BK virus (BKV) in the context of intense immunosuppression. No specific immunosuppressive drug is exclusively associated with PVAN, but most cases reported to date arise while the patient is on triple immunosuppressive combinations, often comprising tacrolimus and/or mycophenolate mofetil plus corticosteroids. Immunologic control of polyomavirus replication can be achieved by reducing, switching, and/or discontinuing components of the immunosuppressive regimen, but the individual's risk of rejection should be considered. The success rate of this intervention is increased with earlier diagnosis. Therefore, it is recommended that all renal transplant recipients should be screened for BKV replication in the urine: 1) every three months during the first two years posttransplant; 2) when allograft dysfunction is noted; and 3) when allograft biopsy is performed. A positive screening result should be confirmed in <4 weeks and assessed by quantitative assays (e.g. BKV DNA or RNA load in plasma or urine). Definitive diagnosis of PVAN requires allograft biopsy. If PVAN and concurrent acute rejection is diagnosed, antirejection treatment should be considered, coupled with subsequently reducing immunosuppression. The antiviral cidofovir is not approved for PVAN, but investigational use at low doses (0.25-0.33 mg/kg intravenously biweekly) without probenicid should be considered for refractory cases. Retransplantation after renal allograft loss to PVAN remains a treatment option for patients clearing polyomavirus replication.

The European Best Practice Guideline group (EBPG) issued guidelines on the evaluation and selection of kidney donor and kidney transplant candidates, as well as post-transplant recipient care, in the year 2000 and 2002. The new European Renal Best Practice board decided in 2009 that these guidelines needed updating. In order to avoid duplication of efforts with kidney disease improving global outcomes, which published in 2009 clinical practice guidelines on the post-transplant care of kidney transplant recipients, we did not address these issues in the present guidelines.The guideline was developed following a rigorous methodological approach: (i) identification of clinical questions, (ii) prioritization of questions, (iii) systematic literature review and critical appraisal of available evidence and (iv) formulation of recommendations and grading according to Grades of Recommendation Assessment, Development, and Evaluation (GRADE). The strength of each recommendation is rated 1 or 2, with 1 being a 'We recommend' statement, and 2 being a 'We suggest' statement. In addition, each statement is assigned an overall grade for the quality of evidence: A (high), B (moderate), C (low) or D (very low). The guideline makes recommendations for the evaluation of the kidney transplant candidate as well as the potential deceased and living donor, the immunological work-up of kidney donors and recipients and perioperative recipient care.All together, the work group issued 112 statements. There were 51 (45%) recommendations graded '1', 18 (16%) were graded '2' and 43 (38%) statements were not graded. There were 0 (0%) recommendations graded '1A', 15 (13%) were '1B', 19 (17%) '1C' and 17 (15%) '1D'. None (0%) were graded '2A', 1 (0.9%) was '2B', 8 (7%) were '2C' and 9 (8%) '2D'. Limitations of the evidence, especially the lack of definitive clinical outcome trials, are discussed and suggestions are provided for future research.We present here the complete recommendations about the evaluation of the kidney transplant candidate as well as the potential deceased and living donor, the immunological work-up of kidney donors and recipients and the perioperative recipient care. We hope that this document will help caregivers to improve the quality of care they deliver to patients. The full version with methods, rationale and references is published in Nephrol Dial Transplant (2013) 28: i1-i71; doi: 10.1093/ndt/gft218 and can be downloaded freely from http://www.oxfordjournals.org/our_journals/ndt/era_edta.html.

Non-adherence with immunosuppressive regimen is a major risk factor for poor outcome after kidney transplantation. Identifying patients at risk for nonadherence requires understanding the risk factors for non-adherence. This prospective study included a convenience sample of 249 adult kidney transplant patients >1 year post-transplant. Non-adherence was monitored electronically using MEMS®. Selected socio-economic, therapy-, patient-, condition-and healthcare team-related risk factors for non-adherence were assessed. Period prevalences were expressed as the percent of prescribed doses taken (taking adherence), the percent of correctly dosed days (dosing adherence), the percentage of inter-dose intervals not exceeding 25% of the prescribed interval (timing adherence), and the number of drug holidays per 100 days (no intake for > 48 h if once daily or for > 24 h if twice daily intake). Testing occurred by simple mixed logistic regression analysis. Factors significant after correction for multiple testing were entered into a multiple logistic regression model. Mean taking, dosing, timing adherence, and drug holidays were 98%, 96%, 93%, and 1.1 days, respectively. Non-adherence was associated with lower self-efficacy, higher self-reported nonadherence, no pillbox usage, and male gender. Adherence declined between Monday and Sunday. This study provides a framework for identifying patients at risk for non-adherence and for developing adherenceenhancing interventions.

Polyomavirus BK (BKV) is the primary cause of polyomavirus-associated nephropathy (PVAN) in kid-

Polyomavirus-associated nephropathy (PVAN) is an emerging disease in renal transplant patients with variable prevalence of 1-10% and graft loss up to 80%. BK virus (BKV) is the primary etiologic agent, but JC virus (JCV) and possibly simian virus SV40 may account for some cases. Intense immunosuppression is viewed as the most important risk factor. However, the preferential manifestation in renal transplants as compared to other allografts or to autologous kidneys of other organ transplants suggests that organ determinants and immunologic factors synergize: Renal tubular epithelial cells and their compensatory proliferation to restore tubular integrity after immunologic, ischemic or toxic injury may provide the critical cellular milieu supporting polyomavirus replication while immune control is impaired due to maintenance immunosuppression, anti-rejection treatment and HLA-mismatches. Patient determinants (older age, male gender, seronegative recipient), and viral factors (genotype, serotype) may have a contributory role. The definitive diagnosis of PVAN requires allograft biopsy which is, however, challenged by (i) limited sensitivity due to (multi-)focal involvement (sampling errors); (ii) varying presentations with cytopathic-inflammatory and/or fibrotic/scarring patterns; (iii) coexisting acute rejection which is difficult to differentiate, but impacts on intervention strategies. Screening for polyomavirus replication in the urine and in the plasma complements allograft biopsy by high sensitivity and allows for noninvasive monitoring. Thus, we suggest a terminology similar to invasive fungal diseases where viruria ("decoy cells") defines patients at risk ("possible PVAN") who should be evaluated for plasma viral load. Increasing BK viremia (>10,000 copies/mL) or urine VP-1 mRNA (>6.5x10(5) copies/ng total RNA) load defines "presumptive PVAN" for which an intervention of reducing immunosuppression should be considered even if the diagnosis could not be confirmed by allograft biopsy ("definitive PVAN"). The response to intervention should be monitored using plasma DNA or urine mRNA load.