BK virus (BKV) plasma dynamics in patients with BKV-associated hemorrhagic cystitis following allogeneic stem cell transplantation

Introduction The use of real-time polymerase chain reaction testing in the investigation of BK virus (BKV)-associated disease has been widely studied in renal transplant recipients; however, far less research has been done in this area with respect to the plasma BK viral load dynamics of BKV hemorrhagic cystitis (BKV-HC) in hematopoietic stem cell transplant recipients. Aim The aim of this study was to examine the BK viral load dynamics in plasma samples collected from patients post transplant who had laboratory-confirmed BKV-HC. Methods Patients who developed BK viremia were compared with patients who did not develop viremia, and a statistical comparison of risk factors for viremia was performed. Seventeen patients were included in this study. Urine samples from the day of BKV diagnosis were available in 13 of the 17 cases. In total, 154 archived plasma samples from around the time of the BKV-HC event were also included in the study from these 17 patients. Results The median time from transplantation to the onset of detectable viremia was 68days. The median viral load in the 13 urine samples was 1.8x108 copies/mL, which was significantly higher than the median viral load in the 38 positive plasma samples of 6.6x102 copies/mL (Mann-Whitney test, U=16, P<0.001). Conclusion The lymphocyte count on the day of the positive BKV test was significantly lower in patients with BKV viremia than in patients with no viremia (P=0.02) and also the white cell and platelet counts were lower on the day of the first positive BKV test. Although there is not inter-patient consistency as regards correlation between urinary BK viral loads and severity of clinical BKV-HC, in individual patients the decline in viral load in plasma did correlate with clinical recovery.