University of Virginia Health System
Medical Laboratories
“Quality You Expect, Service You Deserve”
LABORATORY MEDICINE UPDATE
January 26, 2010
HIV Genotyping and Resistance Reporting
For HIV, resistance interpretation (correlation of Protease and Reverse Transciptase
sequences to antiretroviral drug resistance) is based on interpretation of in vitro and in
vivo phenotypic and virologic response data by The Consensus Panel, an international
expert panel. These include primary and secondary mutations. Siemens Trugene HIV-1
GuideLines Rules 14.0, using data available as of June 2008, is now being applied to the
Molecular Diagnostic Lab HIV Genotyping/Resistance reports. The manufacturer’s
software was installed in July 2009. The update included only one change from the
previous version: the addition of resistance mutation codons for the non-nucleoside
reverse transcriptase inhibitor drug, Etravirine.
HCV Viral Load Testing
The Clinical Microbiology and Molecular Diagnostics Laboratory is now performing
HCV viral load testing (quantitative HCV analysis) with the Roche Diagnostics COBAS
AmpliPrep/TaqMan FDA approved (IVD) method. This real-time PCR method has an
expanded range for quantification (43 – 69,000,000 IU/mL) compared to the method it
replaces. The new assay requires a minimum of 1.2 mL serum. Plasma samples cannot be
used. Test results will be reported in both integer and log base 10 values.
HBV Viral Load Testing
The Clinical Microbiology and Molecular Diagnostics Laboratory will begin performing
HBV viral load testing (quantitative HBV analysis) with the Roche COBAS TaqMan
FDA approved (IVD) method in February 2010. This test will replace the current referral
laboratory test. The new assay requires a minimum of 0.6 mL serum. Plasma samples
cannot be used. The analytical range is 29 – 110,000,000 IU/mL and test results will be
reported as both integer and log base 10 values. This test is to be used for quantification
of HBV DNA in serum of patients with chronic HBV infection and for monitoring
progression of disease and/or response to therapy. The Roche method uses a manual High
Pure System for nucleic acid extraction and real-time PCR for amplification and
detection. The former method performed at Mayo Laboratories was the Siemens
VERSANT branched DNA (bDNA) assay with an analytical range from 357 –
17,900,000 IU/mL. Verification studies performed in the laboratory showed no
significant bias between the two assays.
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New Assay Methodology for Immuno-suppressant Drugs
In June, the Toxicology Laboratory changed from an immunoassay procedure for the
measurement of FK-506 (Tacrolimus, Prograf) and Sirolimus (Rapamune, Rapamycin) to
liquid chromatography/tandem mass spectroscopy (LC/MSMS). The transition to
LC/MSMS is now complete for Cyclosporine as well. Extensive validation of the new
method has taken place and clinicians can expect to see essentially no change in the
values for FK-506, between a 5 and 11% increase for Sirolimus, and a roughly 5%
reduction in values for Cyclosporine. Sample requirements (EDTA-anticoagulated
blood, purple-top tube) and turn-around-time (samples received by 11AM will be resulted
by 5PM) remain the same. Please contact the Toxicology Laboratory (924-2029) or the
Director of the laboratory (pic 3200) if you have any questions.
Appropriate specimens for anaerobic culture
Occasionally the microbiology laboratory receives orders for bacterial culture of
specimens including aspirates, suprapubic urines, kidney/ureteral aspirates, sterile body
fluids, bone tissues and other tissues and biopsies, that only result in the isolation,
identification and susceptibility testing of aerobic bacteria. Because these specimens can
also harbor anaerobic bacteria, the microbiology laboratory will assess the specimen
acceptance in terms of volume and proper collection for anaerobes and plate these
samples for both aerobic and anaerobic bacteria when they are received. An additional
charge will be added for the additional processing required to screen for anaerobic
pathogens.
Specimens for anaerobic culture should be submitted in a sterile black top tube or other
sterile leakproof container such as a cup and sent to the laboratory as soon as possible
after collection. Culturettes are not acceptable for anaerobic cultures.
New Therapeutic Guidelines for Low Molecular Weight Heparin
The Coagulation Laboratory has updated the Low Molecular Weight therapeutic
guidelines that are reported with each LMW Heparin test result. The comment is in
response to the various low molecular weight heparin formulations that are available for
use in the Medical Center.
The new comment is:
Reported units are Anti-Xa U/mL. The Coagulation Laboratory has not established
internal therapeutic guidelines for Low Molecular Weight Heparin. Therapeutic levels are
dependent on timing of dose. Published reference guidelines for venous
thromboembolism in Anti-Xa U/mL: Dalteparin: Peak target 1.05
Enoxaparin, Adult: 0.6 - 1.0
Enoxaparin, Pediatrics: 0.5 - 1.0
Tinzaparin: Peak target 0.85
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Lipoprotein-Associated Phospholipase A2 (PLAC®) Testing Discontinued
Due to concerns about both the technical and clinical performance of this test, the
University of Virginia Medical Laboratories has discontinued this test. Our referral
laboratory, Mayo Medical Laboratories, has also discontinued this test.
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