BK Virus

Clinical Background

BK virus is a polyoma virus in the same family of viruses as human papilloma and JC virus and has become recognized as an important causal infectious agent in complications after kidney transplant.

Epidemiology

Prevalence
- Primary BK infection generally occurs in childhood (without specific symptoms)
  - Most are seropositive by 5 years
- 1-5% of kidney transplant patients are affected
Transmission
- The virus is transmitted via respiratory droplets

Organism

Double-stranded DNA virus
Genetically similar to JC virus
After primary infection, BK virus becomes latent in the kidneys and urinary tract
Reactivated with immunosuppression

Clinical Presentation

Clinical disease is rare in immunocompetent adults
BK virus infections are a cause of morbidity and mortality for patients with hematologic malignancies and transplants
Illnesses caused by BK virus include:
- Nephropathy and graft loss in renal transplant patients
  - BK virus allograft nephropathy (BKVAN) is present in up to 8% of kidney transplant patients
    - Tubulointerstitial nephritis
      - Most common manifestation
      - Leads to irreversible graft failure in 40-50% of patients
  - New immunosuppressive regimens may increase the risk of BKVAN
- Hemorrhagic cystitis and renal impairment in patients with hematologic malignancy and bone marrow transplant

Treatment

Bone marrow/hematologic malignancies
- Supportive in hemorrhagic cystitis; most patients recover
- Refractory cystitis may be catastrophic
  - Poor response to antiviral therapy
Renal transplant
- If no active rejection present, judicious reduction of immune suppression is acceptable and usually decreases viral load

Indications for Laboratory Testing

Tests generally appear in the order most useful for common clinical situations
Click on number for test-specific information in the ARUP Laboratory Test Directory

Test Name and Number	Recommended Use	Limitations	Follow Up
BK Virus, Quantitative PCR 0090067 Method: Polymerase Chain Reaction	Exclude diagnosis of BKVAN Monitor patient response to treatment	Negative result does not rule out the presence of PCR inhibitors in the patient specimen or BK virus DNA concentrations below the level of detection by the assay Inhibition may also lead to underestimation of viral quantitation	Renal allograft biopsy is required to make a definitive diagnosis of BKVAN
BK Virus, Quantitative and Qualitative Detection by PCR, Blood 2002304 Method: Polymerase Chain Reaction	Detect BK virus infection and viral load quantitation	Negative result does not rule out the presence of PCR inhibitors in the patient specimen or BK virus DNA concentrations below the level of detection of the assay Inhibition may also lead to underestimation of viral quantitation
BK Virus, Quantitative and Qualitative Detection by PCR, Urine 2002310 Method: Polymerase Chain Reaction	Detect BK virus infection and viral load quantitation	Negative result does not rule out the presence of PCR inhibitors in the patient specimen or BK virus DNA concentrations below the level of detection of the assay Inhibition may also lead to underestimation of viral quantitation
Cytology, Urologic 8209704 Method: Routine Cytopathologic Evaluation	May be helpful if negative, but PCR and biopsy are more sensitive	Positive test does not necessarily diagnose BKVAN	Biopsy or PCR is advised for positive test
Immunohistochemistry Stain Offering arup005 Method: Immunohistochemistry	For fixed tissue samples, consultative services as well as immunohistochemical staining for the presence of BK virus are available