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Laboratory Medicine Updates - February 13, 2004

University of Virginia Health System

Medical Laboratories

“Quality You Expect, Service You Deserve”


February 13, 2004

Changes to Standing Orders Process

The Medical Laboratories has modified the allowable time for active Standing Orders. The maximum length of time that a Standing Order may be considered valid has changed from 6 months to 1 year. The following information must be provided in writing on an out-patient laboratory request form or a prescription slip for a standing order to be accepted by the lab:

· Patient Name

· Medical Record or Account Number

· Physician Name and Signature

· Patient Location

· Test(s) ordered

· Frequency of the test

· Dated duration of the order (no longer than 1 year, must include start and stop date of order)

· Diagnosis code associated with each test ordered

· “Standing Order” must be written on the order form



Change in Reference Interval for TSH (Thyroid Stimulating Hormone)


Based on recent recommendations (Journal of the American Medical Association, 291:228-238, 2004), the reference interval for TSH has been adjusted to 0.45 – 4.5 mIU/L. Please note there is also a change in the reporting units from microIU/mL to mIU/L. This change has no effect on the absolute number. This change will be reflected on results effective February 17, 2004.

Reference Interval/Therapeutic Range Changes: aPTT and PT

Effective February 3, 2004, the Coagulation Laboratory will be changing the Heparin therapeutic range to reflect the new reagent changes in the aPTT assay.  The new heparin aPTT therapeutic range is 71 to 103 seconds which corresponds to 0.3 - 0.7 Anti-Xa Units/mL.

The aPTT and PT reference intervals will remain the same:  24.9 to 35.3 seconds for the aPTT assay and 12.2 to 15.3 seconds for the PT assay.   The new PT reference mean for INR calculation is 13.9 with an ISI value of 1.39.  For clarification, please contact the Special Coagulation Laboratory at 434-924-8007.


HIV-1 p24 Antigen Test No Longer Available


Due to a decision by the vendor to no longer provide reagents for HIV-1 p24 Antigen testing, this test has been discontinued nationally. The recommendation for follow-up testing after a positive HIV Western Blot is for a quantitative HIV (Ultrasensitive HIV Viral Load), performed by the Molecular Diagnostics Laboratory. Please note that the Viral Load test can only be performed on plasma samples.




Fetal Fibronectin (fFN) Test Now Available


Testing for fetal Fibronectin for cases of suspected pre-term labor is now available through the UVa Core Laboratory. Specific training in specimen collection has been provided to the OB physicians and specimen collection devices are available only in those areas (Labor and Delivery, PCC OB/GYN clinic, and Northridge OB/GYN clinic).




Testosterone Testing


The analysis of testosterone levels is now being performed in the Davis Laboratory. Testing will now be performed Monday through Friday. Samples received by 10 AM will have results available by 4 PM.




Update on Flu Testing


Beginning on January 26, 2004 at 0700, the Microbiology Division of Medical Laboratories has resumed both rapid flu and flu culture testing with no restrictions.




Cryoglobulin Analysis


The minimum volume for this test is 2 mL serum.  Proper collection and handling prior to analysis is critical.  Specimens (gold tops) should be placed in a cup of warm water or next to a gel-based heel warmer for transport to the laboratory.

What’s tested for in a “Drugs of Abuse” Screen?


The standard Drugs of Abuse Screen in urine (DAU) tests for sample integrity (pH, specific gravity, and creatinine) and the drugs/classes of drugs listed below. A positive screen for any of these compounds will automatically result in confirmation testing by gas chromatography or gas chromatography/mass spectroscopy.

  • Delta-9 THC (active metabolite of marijuana)
  • Benzoylecgonine (metabolite of cocaine)
  • Amphetamine/methamphetamine
  • Benzodiazepines
  • Opiates
  • Barbiturates
  • Phencyclidine (PCP)
  • Ethanol
  • Propoxyphene


NOTE: If synthetic opioid use/abuse is suspected (eg: hydromorphone, oxycontin, etc.), please note this on the transmittal. If methadone is suspected, please order Urine Methadone Screen (UMTHD). If both the common drugs of abuse above and methadone testing are required, both a DAU and a Urine Methadone Screen should be ordered.