Definitions of possible, probable/presumptive, and proven BK virus (BKV) nephropathy
| Consensus group | Possible | Probable/presumptive | Proven |
|---|---|---|---|
| AST-IDCOP [38] | High levels of DNAuria, VP1 mRNA, decoy cells or Haufen reflecting high urinary viral levels | Probable: >1,000 plasma, VCN/mL twice in 3 weeks Presumptive: >10,000 plasma, VCN/mL in 1/2 measurements |
Viral identification with IHC or ISH, tubular cell cytopathic features |
| Basel Working Group [39] | Urinary viral DNA or RNA, decoy cells or viral particles (Haufen) | >10,000 plasma VCN/mL in 1 measurement or >650,000 urine VP1 mRNA copies/ng total RNA for 3 weeks | Viral identification by IHC or ISH, or viral particles by EM, and tubular cell cytopathic features |
| European Renal Association-EDTA [40] | 1,000 to 10,000 plasma VCN/mL, requires monitoring every 2–4 weeks | >10,000 plasma VCN/mL or >10,000,000 urinary VCN/mL | Viral identification by IHC and tubular cell cytopathic features |
| ESCMID [41] | None | >10,000 plasma VCN/mL in 1 measurement | Viral identification by IHC or ISH and tubular cell cytopathic features |
| BKV Transplantation Associated Viral Working Group [37] | None | • Significant plasma VCN on repeated measurements • Immunosuppression treatments • >20% Rise in serum creatinine level from baseline • No or inadequate kidney biopsy • No other process to explain the above |
Viral identification by IHC or ISH |
| Banff Working Group [42,43] | None | None | Tubular cell viral cytopathic changes and/or positive IHC |
| American Society of Nephrology [44] | None | >10,000 plasma VCN/mL in 1 measurement | None |
AST-IDCOP, American Society of Transplantation Infectious Diseases Community of Practice; VCN, DNA viral copy number; IHC, immunohistochemistry for simian virus 40 large T antigen; ISH,
a)“Proven” requires findings from a kidney biopsy.