BK Virus, Molecular Detection, Quantitative, PCR, Plasma
As a prospective and diagnostic marker for the development of nephropathy in renal transplant recipients
Real-Time Polymerase Chain Reaction (PCR)/DNA Probe Hybridization
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
BK Virus PCR, Quant, P
BK (polyoma) virus
BKV Quantitative DNA
BKV Quantitative DNA
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Lavender top (EDTA)
Specimen Volume: 1 mL
Collection Instructions: Separate plasma within 24 hours of collection.
Forms: If not ordering electronically, submit a Microbiology Request Form (Supply T244) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Plasma EDTA||Refrigerated (preferred)||7 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Polyomaviruses are small (45 nm, approximately 5,000 bp), DNA-containing viruses and include 3 closely related viruses of clinical significance, SV-40, JC virus (JCV), and BK virus (BKV). SV-40 naturally infects rhesus monkeys but can infect humans, while BKV and JCV cause productive infection only in humans.(1,2) Acquisition of BKV begins in infancy. Serological evidence of infection by BKV is present in 37% of individuals by 5 years of age and over 80% of adolescents.
BKV is an important cause of interstitial nephritis and BKV-associated nephropathy (BKVAN) in recipients of kidney transplants. Up to 5% of renal allograft recipients can be effected about 40 weeks (range 6-150) post-transplantation.(3) Quantitative PCR analysis of BKV DNA in the plasma is the most widely used blood test for the laboratory diagnosis of BKV-associated nephropathy. Importantly, the presence of BKV DNA in blood reflects the dynamics of the disease: the conversion of plasma from negative to positive for BKV DNA after transplantation, the presence of DNA in plasma in conjunction with the persistence of nephropathy, and its disappearance from plasma after the reduction of immunosuppressive therapy.(4-8) The presence of BKV DNA in plasma at levels > or =10,000 copies BKV DNA/mL may correlate with an increased risk of BKVAN with this assay. Furthermore, the trend of viral DNA quantitation (eg, increasing, decreasing) may be helpful in predicting the onset of BKVAN.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Increasing copy levels of BK virus (BKV) DNA in serial specimens may indicate possible BKV- associated nephropathy (BKVAN) in kidney transplant patients.
Viral loads >10,000 copies/mL in plasma may also indicate a risk for BKVAN.
This assay does not cross react with other polyomaviruses, including JC virus and SV-40.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Serial monitoring of viral loads may be indicated to assess changing levels of BK virus (BKV) DNA.
Qualitative results are available as LCBKP/89982 BK Virus, Molecular Detection, PCR, Plasma.
This test is not to be used to screen healthy patients. It is to be used for patients with a clinical history or risk factors for BKV disease. Depending on the population, varying percentages of patients may be found to be positive.
Results from this real-time PCR assay on the LightCycler (LC PCR) were compared to a previous PCR assay (directed to VP2 region of the polyoma virus based on a published method) on 112 plasma specimens and 108 urine specimens. Using the previous method as the gold standard, the diagnostic sensitivity and specificity is 94% and 90% for plasma and 100% and 100% for urine, respectively. The discrepant specimens had low viral DNA copy numbers (<5,000 copies/mL), which is associated with greater variability of quantitative results.
Supplemental Data (Spiking Studies):
To supplement the above data, 30 negative plasma and urine specimens were spiked with BKV-positive control plasmid at the approximate limit of detection (LoD). The 30-spiked specimens were run in a blinded manner along with 57 plasma and 58 urine negative (nonspiked) specimens. 100% of the spiked specimens were positive and 100% of the nonspiked specimens were negative.
Analytical Sensitivity/Limit of Detection (LoD):
The lower LoD of this assay is 244 DNA target copies per mL in urine and plasma.
No PCR signal was obtained from the extracts of a variety of human viruses that can be found in urine or plasma, including cytomegalovirus, Epstein-Barr virus, human herpesvirus-6, enterovirus, adenovirus, and mumps virus.
Qualitative inter-assay and intra-assay precision were 100%. Quantitative values had a standard deviation of <0.25 log10 across the analytical measuring range.
The reference range of BKV in plasma is "None Detected." This test is not to be used to screen healthy patients. It is to be used for patients with a clinical history or risk factors for BKV associated nephropathy.
Reportable Range (lower and upper limits of quantification, analytical measurement range):
Reportable range is from 5,000 to 5,000,000 copies/mL. The assay demonstrates acceptable linearity between these values.
Viral nucleic acid is extracted by the MagNA Pure automated instrument (Roche Applied Science) from clinical specimens. Primers are directed to the large T antigen gene, which is a conserved sequence specific for BK virus (BKV). This assay detects only BKV; it does not detect JC virus or SV-40 (other polyoma viruses). The LightCycler instrument (Roche Applied Science) amplifies and monitors the development of target nucleic acid sequences after the annealing step during PCR cycling. This automated PCR system can rapidly detect (30-40 minutes) amplicon development through stringent air-controlled temperature cycling and capillary cuvettes. The detection of amplified products is based on the fluorescence resonance energy transfer (FRET) principle. For FRET product detection, a hybridization probe with a donor fluorophore, fluorescein, on the 3'-end is excited by an external light source and emits light that is absorbed by a second hybridization probe with an acceptor fluorophore, LC-Red 640, at the 5'-end. The acceptor fluorophore then emits a light of a different wavelength that can be measured with a signal that is proportional to the amount of specific PCR product. Quantitative standards are used to develop a standard curve. Specimens with unknown levels of BKV DNA are then compared to the standard curve to determine the copy level of the virus. Reportable range is from 5,000 copies/mL to 5,000,000 copies/mL.(Unpublished Mayo method)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Saturday; Varies
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Same day/1 day
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.