Monitoring of BK virus replication in the first year following renal transplantation.
BACKGROUND
BK virus-associated nephropathy (BKVAN) is one of the most common viral diseases affecting renal allografts. Screening for viral replication may allow for earlier intervention with reduced allograft loss. A plasma viral load >10(4) copies/mL of BKV DNA is recommended for a presumed diagnosis of BKVAN.


METHODS
We monitored BKV load on serum and urine samples by Real-Time TaqMan PCR in 229 renal transplant recipients in the first year post-transplantation. Overall, 2025 serum and 2025 urine samples were evaluated. A graft biopsy was performed in 47/229 patients to investigate the declining renal function. Operating characteristics [sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV)] and receiver operating characteristic (ROC) curve analysis at different viral load values were calculated.


RESULTS
Serum BKV viral load was >10(4) in 5/229 patients (2.2%). A histological diagnosis of BKVAN was made in 3/229 patients (1.3%): 3/5 (60.0%) among those with serum viral load >10(4) and 3/4 (75.0%) in those with >1.6 x 10(4). Operating characteristics of a serum BK load of 10(4) for the diagnosis of BKVAN were as follows: sensitivity, 100%; specificity, 99.1%; NPV, 100%; PPV, 59.4%. Specificity and PPV rose to 99.6% and 75.0% when using a cut-off level of 1.6 x 10(4) copies/mL.


CONCLUSIONS
The recommended level of BK viraemia of 10(4) copies/mL is useful to identify patients at risk of BKVAN, although specificity and PPV increase by using a cut-off level of 1.6 x 10(4) copies/mL. BK replication may occur in the first 3 months post-transplantation and subsequently recede. Therefore, the temporal profile of BKV replication has to be accurately evaluated and occasionally elevated values should prompt a closer monitoring.
Costa
Cristina
C
Dipartimento di Sanità Pubblica e Microbiologia, Laboratorio di Virologia, Università di Torino, Italy. cristina.costa@unito.it
Bergallo
Massimiliano
M
Astegiano
Sara
S
Terlizzi
Maria Elena
ME
Sidoti
Francesca
F
Segoloni
Giuseppe P
GP
Cavallo
Rossana
R
D000328:Adult; D000368:Aged; D001739:BK Virus / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity / Q000502:physiology*; D016022:Case-Control Studies; D004279:DNA, Viral / Q000097:blood / Q000235:genetics / Q000652:urine; D005260:Female; D006801:Humans; D007674:Kidney Diseases / Q000209:etiology / Q000473:pathology / Q000821:virology; D016030:Kidney Transplantation / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D027601:Polyomavirus Infections / Q000209:etiology / Q000821:virology; D012372:ROC Curve; D012307:Risk Factors; D013997:Time Factors; D014412:Tumor Virus Infections / Q000209:etiology / Q000821:virology; D014766:Viremia / Q000209:etiology / Q000821:virology; D014779:Virus Replication
D004279:DNA, Viral