Prediction of BK Viremia by Urine BK Viral Load in Renal Transplant Patients: BK Viral Load Results in Paired Urine and Plasma Samples
1Pathology, University of New Mexico, Albuquerque, NM
2Microbiology, Tricore Reference Laboratories, Albuquerque, NM.
Meeting: 2018 American Transplant Congress
Abstract number: C193
Keywords: Infection, Kidney transplantation, Nephropathy, Screening
Session Information
Session Name: Poster Session C: Kidney: Polyoma
Session Type: Poster Session
Date: Monday, June 4, 2018
Session Time: 6:00pm-7:00pm
Presentation Time: 6:00pm-7:00pm
Location: Hall 4EF
BK virus (BKV) associated nephropathy (BKVAN) affects up to 10% of renal transplant recipients, causing graft failure without intervention; a presumptive BKVAN diagnosis is made with sustained plasma BKV >4 log10 copies/mL. BKV screening is recommended in the first post-transplant year; however testing urine versus plasma is controversial. In this study we analyzed a large data set of paired urine and plasma BK viral load results in renal transplant patients. Our goal was to identify correlations between urine and plasma BKV levels to establish urine BKV cutoffs to predict BKV viremia.
The WHO BKV International Standard was used to calculate the conversion factor to IU/mL. ROC curve analysis evaluated urine BKV as the continuous variable and plasma BKV >2.6 log IU/mL (limit of quantification (LOQ)) or plasma BKV ≥4.0 log IU/mL (clinical cutoff) as binary values. BK viremia and critical BK viremia were defined as plasma BKV ≥2.6 log IU/mL and ≥4 log IU/mL respectively.
From January 2013 to April 2017, 1030 paired urine and plasma BKV results were analyzed. Urine BKV 4.0 log IU/mL predicted BK viremia (98.7% sensitivity, 70.8% specificity, 99.7% negative predictive value (NPV), 37.8% positive predictive value (PPV)). Urine BKV 6.7 log IU/mL predicted critical BK viremia (100% sensitivity, 92.1% specificity, 100% NPV, 50.3% PPV). We used these cutoffs and the urine viral load LOQ to create four groups.
| Group | Urine BKV(Log IU/mL) | # Sample Pairs | Plasma BKV (Log IU/mL) | ||
| <2.6 (%) | 2.6-3.9 (%) | ≥4.0 (%) | |||
| 1 | <2.4 | 441 | 100 | 0 | 0 |
| 2 | 2.4-3.9 | 179 | 98.6 | 1.4 | 0 |
| 3 | 4.0-6.6 | 259 | 88.5 | 11.5 | 0 |
| 4 | ≥6.7 | 151 | 21.5 | 28.2 | 50.3 |
As urine BKV increased, the chance of BK viremia increased; no critical BK viremia was seen until Group 4. In Group 4, the PPV for BK viremia was 78.5%, with a PPV 50.3% for critical BK viremia.
Post-transplant BKVAN monitoring is complicated by high sensitivity/early detection urine testing versus high specificity/late detection plasma testing; testing both contribute unnecessarily to medical costs. Our study is the first to suggest a novel model to maximize sensitivity, specificity and cost efficiency by first testing only urine BKV until it reaches 4.0 log IU/mL, then only testing plasma BKV.
CITATION INFORMATION: Madden K., Janitell C., Yang S. Prediction of BK Viremia by Urine BK Viral Load in Renal Transplant Patients: BK Viral Load Results in Paired Urine and Plasma Samples Am J Transplant. 2017;17 (suppl 3).
To cite this abstract in AMA style:
Madden K, Janitell C, Yang S. Prediction of BK Viremia by Urine BK Viral Load in Renal Transplant Patients: BK Viral Load Results in Paired Urine and Plasma Samples [abstract]. https://atcmeetingabstracts.com/abstract/prediction-of-bk-viremia-by-urine-bk-viral-load-in-renal-transplant-patients-bk-viral-load-results-in-paired-urine-and-plasma-samples/. Accessed May 16, 2025.« Back to 2018 American Transplant Congress