Laboratory Medicine Updates - April 26, 2004
University of Virginia Health System
“Quality You Expect, Service You Deserve”
LABORATORY MEDICINE UPDATE
April 26, 2004
Due to the increased volume in glucose tolerance testing, the Medical Laboratories will now schedule glucose tolerance tests in both the Primary Care and Barringer collection sites. The number to make an appointment for both sites is 434-924-5288.
Changes in Reference Intervals
Bilirubin: The upper limit of the reference interval for Total Bilirubin (ADULTS only) has been adjusted to 1.2 mg/dL. The new reference interval is 0.3 to 1.2 mg/dL.
Vancomycin: In response to a request from the Pharmacy and Therapeutics Committee, the following are new reference (target) intervals for trough vancomycin levels:
Target value: 8 – 15 µg/mL
Toxic (Critical) value: >20 µg/mL
Digoxin: The reference (target) interval for Digoxin has been changed to 0.5 – 1.0 ng/mL. The toxic (critical) value will remain the same at 2.0 ng/mL.
The reference interval for Free (unbound) Digoxin has been changed to 0.4 to 0.8 ng/mL. The reflex level for performing the free Digoxin test (only if the total Digoxin is >2.0ng/mL) remains the same.
Requests for Read-Back of Critical and Toxic Values
In January 2004, JCAHO expanded the 2nd National Patient Safety Goal “Improve the Effectiveness of Communication among Caregivers” to include a read-back of verbally communicated critical test results. This is an important feature in ensuring the correct information is reported by the laboratory and properly interpreted by the caregiver. This protocol helps to ensure patient safety and effective treatment and diagnosis. The UVA Medical Laboratories now requires that a read-back of patient names and any critical or toxic value be obtained and documented as part of the Medical Record to show compliance with this new requirement. Cooperation with this request is greatly appreciated.
Change in Molecular Diagnostics Laboratory’s Services
The laboratory will no longer offer molecular-based HLA typing for clinical specimens. Specimens regarded as investigational or for research use only will be accepted for HLA typing for Class I (A,B,C) or Class II (DR,DQ) by DNA methods and must be billed to a Principal Investigator’s Grant Account. Clinical HLA samples will now be sent via our referral laboratory Quest Diagnostics to the Blood Center of Southeastern Wisconsin Laboratory.
Immunohistochemical Assay for Epidermal Growth Factor Receptor
A malignant neoplasm results from uncontrolled or dysregulated cellular proliferation. That process reflects a disturbance in the balance between growth-promoting and growth-inhibiting biological factors. In normal tissues, those influences allow cells to grow in a controlled and regulated fashion, maintaining normal cellular integrity and function. Malignant cells evade such controls, using a variety of mechanisms, and aberrant growth occurs. One important driver for the growth of certain cellular populations is known as epidermal growth factor (EGF); this factor and its receptor (EGFR) are felt to play a role in the development and progression of several human malignancies. These include carcinomas of the lung, breast, prostate, colon, ovary, and head and neck.
Recently, a chimeric (mouse/human) monoclonal antibody has been developed—known as cetuximab—which binds to EGFR and prevents its response to EGF. This agent has passed preliminary clinical trials and has been approved by the Federal Food & Drug Administration (FDA) for therapeutic use in selected oncological settings. In particular, it has proven to be useful in producing beneficial effects when given with a drug known as irinotecan to patients with metastatic colorectal carcinoma. It also may have some use as a single therapeutic agent if irinotecan cannot be tolerated.
In order to be eligible for treatment with cetuximab, patients must have their tumor tissues tested by immunohistochemical means for EGFR expression. A kit has been FDA-approved and marketed for this purpose, and it is now available through the University of Virginia Medical Laboratories. Tissue sections of biopsies or resection specimens of suitable tumors are prepared and labeled with an antibody to EGFR. Possible binding of that reagent is visualized with a chromogenic dye and interpreted by the pathologist, using predetermined histological criteria. Positive and negative control tissues are studied concurrently for comparison. If a given tumor is interpreted as reactive for EGFR, the patient will be eligible to receive cetuximab. On the other hand, if the tumor lacks EGFR, there would be no therapeutic benefit in administering that agent.
EGFR immunohistochemistry will be performed twice per week (Tuesday & Thursday) and the results will be appended to surgical pathology reports as is currently done for other predictive tumor markers (e.g., HER-2/neu, estrogen receptor protein, progesterone receptor protein). This process will follow the issuance of data on the morphological characteristics of any given tumor.
Questions on this procedure may be directed to Dr. Stacey E. Mills (2-4406; firstname.lastname@example.org); Dr. Mark H. Stoler (2-0284; email@example.com); Dr. Christopher Moskaluk (2-4408; firstname.lastname@example.org) or Dr. Mark R. Wick (4-9038; email@example.com).