Laboratory Medicine Updates - December 21, 2003

 

 

University of Virginia Health System

Medical Laboratories

“Quality You Expect, Service You Deserve”

 

LABORATORY MEDICINE UPDATE

 

December 21, 2003

 

Recommendations and Availability of Testing for Influenza A/B

 

Due to the high incidence rate of influenza in Virginia and the national shortage of diagnostic kits and tissue culture supplies to detect influenza A and B, current recommendations are that testing of outpatient specimens for influenza be suspended.  Patients with signs and symptoms compatible with flu should be considered positive.  Influenza viral diagnostic testing should be reserved for patients admitted to the hospital and employees with flu-like illness. 

 

Therefore, testing for Influenza will no longer be performed on Outpatients as of Dec. 22, 2003 unless approved by the Director-on-Call of Clinical Microbiology at PIC 1221or by contacting Medical Laboratories Customer Service at 434-924-5227.  If a sample is received for Influenza testing on an Outpatient who is not being admitted to the hospital and / or has not been approved by the Microbiology Director on call, the test will be cancelled and the physician will be notified.

 

 

Cytogenetics Laboratory Weekend Coverage

 

The Cytogenetics Laboratory’s regular hours are from 8 A.M. - 4:30 P.M., Monday through Friday.  From 5 P.M. on Friday until 8 A.M. on Monday, there is a cytogenetics laboratory technologist on call.  Arrangements for weekend processing of bone marrow and STAT blood samples can be made by paging the Clinical Pathology Resident on-call at pic 1383.  Please note that most cytogenetic samples can tolerate being held overnight or over a weekend refrigerated or at room temperature without compromise.

 

When calling for weekend service, please have available the following information:

  • Patient’s name
  • Hospital medical record number
  • Attending physician name and pic number
  • Sample type and time and location of collection

 

In consultation with the Division of Medical Genetics, appropriate processing and initial testing will be arranged.

 

 

 

 

 

C-Reactive Protein Testing

 

The Medical Laboratories offer two tests for C-Reactive Protein (CRP).

  • CRP testing to assess inflammation status (test code CRP) is reported in mg/dL and is reported down to 0.1 mg/dL.
  • High sensitivity CRP testing (test code HSCRP) is reported in mg/L and is appropriate for assessing risk of cardiovascular disease only.  This test is reported down to 0.1 mg/L.

 

 

Paraffin Section Fluorescence in situ hybridization (FISH) for her 2/neu / c-erbB2 in breast carcinoma and in other tumors

 

The Surgical Pathology Division has validated performance of a new automated platform in the Histology Laboratory for her 2/neu FISH.  The assay uses a large DNA probe directed against the HER2 gene, the target of Herceptin therapy.  This assay performed very well on formalin fixed paraffin embedded cell lines that are used as controls.  In addition validation FISH assays have been performed on selected tumors including a tumor that was more than 15 years of age in which slides cut 15 years ago and stored at room temperature still provided excellent signals. 

 

In any situation in which her 2/neu amplification is shown to be clinically relevant, FISH for her 2/neu amplification is now the preferred test rather than immunohistochemistry and will be performed.  In particular, in the reflex analysis of invasive breast carcinoma for ER/PR and her 2/neu expression, ER and PR will continue to be ordered by immunohistochemistry and signed out routinely whereas her 2/neu will be done by FISH rather than immunohistochemistry.  Note that there will be a few cases in which immunohistochemistry may still be appropriate.  For example, in the potential selection for Herceptin therapy for tumors other than breast carcinomas, such as some ovarian tumors or other rare adenocarcinomas, both assays may be appropriate since the mechanism of her 2/neu over expression in those settings may not be related to gene amplification.

 

 

New in situ hybridization assays in Anatomic Pathology

 

Epstein Barr Virus / EBER messenger RNA in situ hybridization

It is well established in the literature that EBER messenger RNA is the most sensitive and specific method for detecting latent Epstein Barr Virus infection which is frequently associated with immunosuppression, transplantation and selected lymphoid as well as epithelial neoplasms.  EBER-mRNA in situ hybridization is superior to immunohistochemistry for Epstein Barr virus (EBV) latent membrane protein expression.  The new assay has been shown to be highly specific in that it exhibits no cross-reaction with cells heavily infected with Herpes Simplex Virus.  The assay is now available for adjunctive clinical use in cases of Hodgkin lymphoma, transplant related lymphoproliferative disorders, lymphoma associated with immunosuppression, selected cases of epithelial malignancies such as lymphoepithelioma or gastric adenocarcinoma.

 

 

 

Kappa/Lambda messenger RNA expression by in situ hybridization

An in situ hybridization assay for Kappa and/or Lambda messenger RNA expression has recently bee implemented.  The probes are a cocktail of oligonucleotides directed against consensus portions of the Kappa and Lambda light chains.  Internal validation studies demonstrated highly specific detection of light chain messenger RNA using tonsilar and lymph node controls.   The limitation of this assay is one of sensitivity as with all reagents available for this test.  Thus a positive result is very helpful but a negative result is relatively meaningless.  In the workup for B-cell clonality the pathologist may suggest performing both immunohistochemical as well as light chain assays until the clinical performance of this new assay is better established.