Quantitative viral load measurement for BKV infection in renal transplant recipients as a predictive tool for BKVAN

Infection by polyomavirus BK (BKV) is an emerging problem in the clinical management of renal transplant patients
because it is responsible for nephropathy and consequently can cause loss of the transplanted organ (BKV associated
nephropathy, BKVAN).
Aim of this study was to evaluate the use of blood viral load measurement as a screening tool for diagnosis of BKV
infection and to identify a threshold value for the management of patients.
A total of 75 kidney transplant patients, corresponding to 338 consecutive plasma samples, were analyzed by an automatic
system for nucleic acid extraction and quantitative real-time polymerase chain reaction (PCR) for detection
of BKV. BKV was detected in 170 samples (26 patients) with a median viral load of 4.1 log10 copies/mL; among these
26 patients, seven (34.7%) were found to have BKVAN on allograft biopsy together with a median viral load of 5 log10
copies/mL. The ROC curve analysis identified a viral load equal to 4.1 log10 copies/mL as the best discriminant cut-off
value to predict the disease and to identify patients at risk of developing BKVAN.