Welcome to the Interpretive Guide. This Guide provides information relating to test selection, utilization, and interpretation. The Guide is continually updated by adding new information and modifying posted information. All information is based on peer-reviewed publications, practice guidelines, or other reputable sources and is intended to be without promotional considerations.

Reference ranges are provided for your convenience and are based on Quest Diagnostics data or published references (where cited). These ranges can serve as a guideline; however, interpretation of patient results should be based on the ranges provided in the patient report.

Included in the Interpretive Guide are four types of information:

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Test highlights and summaries provide a review of clinical use and background, methodology, specimen requirements, and interpretation of the test.

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Test guides provide testing algorithms or other information that assists in appropriate test selection.

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Technology guides compare multiple technologies provided for the same or similar analytes.

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What's New

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Resistance to Thyroid Hormone (RTH) includes an algorithm for the differential diagnosis of hyperthyroxinemia and nonsuppressed TSH, which may be caused by mutation of the thyroid hormone receptor beta gene.

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The EGFR Pathway (KRAS with Reflex to NRAS, BRAF) test is used to assess eligibility and potential for response to treatment with epidermal growth factor (EGFR) antagonists in patients with metastic colorectal cancer.

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ER/PR/HER-2 immunohistochemistry (IHC) testing options are detailed in our new test guide. Options include manual or semi-automated interpretation of stained slides. Interpretation can be performed at Quest Diagnostics or at the client site.

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Laboratory Testing in the Management of HIV Infection: this test guide is based on DHHS guidelines for use of laboratory tests at various stages of HIV infection. Information that may help timing and appropriate selection of laboratory tests is provided.