BK Virus, PCR, Quantitative, Plasma is intended to be used for immunosuppressed patients, mainly renal transplant recipients and hematopoietic stem cell/bone marrow transplant recipients.  It is not intended for use in immunocompetent patients.

Primary infection with BK virus generally occurs during childhood without specific symptoms.  Symptoms that may occur include fever or a non-specific upper respiratory infection.  Infection is widespread, with approximately 90% of adults seropositive globally.  The virus remains latent in the urogenital tract and hematolymphoid tissues, but reactivation can occur.



In immunosuppressed patients, BK virus reactivation has been associated with hemorrhagic cystitis in hematopoietic stem cell/bone marrow transplant recipients and in patients with ureteral stenosis.  In renal transplant recipients, BK virus-associated nephropathy may lead to allograft failure.  According to retrospective studies, BK virus nephropathy develops in 1 to 5 percent of renal-transplant recipients, with loss of allograft function occurring in about half the cases.  BK virus-specific antiviral therapy is not currently available.  In some cases, BK virus replication may be controlled by reducing the level of maintenance immunosuppression therapy, though this change may result in an increased risk of subsequent rejection. 



Detected BK DNA is reported quantitatively as follows

    < 40 IU/mL (< 1.6 Log10 IU/mL): Detected, but below the Lower Limit of Quantitation (outside the linear range, no quantitative value reported).

     40 IU/mL (1.6 Log10 IU/mL) – 100,000,000 IU/mL (8.0 Log10 IU/mL): reported as quantitative value, within linear range. 

     >100,000,000 IU/mL (> 8.0 Log10 IU/mL): Detected, but above the Higher Limit of Quantitation (outside the linear range, no quantitative value reported).



The Analytical Measurement Range is 40 to 100,000,000 (1.6 to 8.0 Log10) IU/mL. Results below 40 IU/mL may not be reproducible due to low copy number. The lower limit of detection is 22 (1.3 Log10) IU/mL.

1. The lower limit of detection is 22 (1.3 Log10) IU/mL.  A negative result does not exclude the possibility of BK Virus infection since very low levels of infection or sampling error may cause a false negative result. 

2. Use of liquid anticoagulants may yield up to 15% dilution effect (lower values) as compared to lyophilized anticoagulants.  Consistent choice of specimen collection tube-type is recommended. 

3.  Changes in DNA sequence due to nucleotide polymorphism or mutation at the primer or probe binding site may cause false negative results.  Primer or probe mismatch may also be due to subtype-associated polymorphism.

Testing is performed using the FDA-approved Roche Cobas system. This is a quantitative real-time PCR test.