Diagnostic, Monitoring and Resistance Laboratory Tests for HIV

From New York State Department of Health AIDS Institute

January 2014

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Table of Contents

Editor's Note

Diagnostic HIV laboratory tests and interpretation algorithms evolve; individual laboratories have internal protocols for reporting tests with preliminary results. Indeterminate, inconclusive, non-diagnostic, and pending validation are among the terms used when preliminary results cannot be classified definitively. The clinician should contact the appropriate laboratory authority to determine the significance of the non-definitive results and the supplemental testing that would be indicated. This is of particular importance with tests from pregnant women, newborn children, and patients with suspected acute HIV infection or HIV-2. Clinicians should become familiar with the internal test-reporting policies of their institutions.

Important Note (October 2013)

A new HIV diagnostic testing algorithm has been verified through scientific studies and offers several advantages over the traditional enzyme immunoassay (EIA)-Western blot algorithm, including earlier and more accurate detection of HIV infections, the ability to differentiate between HIV-1 and HIV-2 infections, and lower costs. Recommendations for its use are anticipated from the Centers for Disease Control and Prevention (CDC). The New York State Department of Health (NYSDOH) has issued a Dear Colleague letter to update clinicians about this new algorithm. This guideline is currently in the process of being updated to include information regarding the new algorithm.

Important Notes (June 2013)

Clinicians should obtain a plasma HIV RNA assay to exclude HIV infection when there is a discrepancy between an HIV screening test and an HIV confirmatory test, such as the Western blot. See the New York City Department of Health and Mental Hygiene Health Advisory: Missed Opportunity to Detect Acute HIV Infection.
The New York State Department of Health (NYSDOH) has issued interim guidelines for New York State-Permitted Clinical Laboratories regarding use of a new laboratory testing algorithm for the diagnosis of HIV infection. Refer to the NYSDOH Letter: Interim Guidelines on the Use of a New Diagnostic Testing Algorithm for HIV Infection.

Key to Abbreviated Terms
bDNA	Branched chain DNA
CDC	Centers for Disease Control and Prevention
CIA	Chemiluminescent immunoassay
EIA	Enzyme immunoassay
ELISA	Enzyme-linked immunosorbent assay
FDA	US Food and Drug Administration
HLA	Human leukocyte antigen
NAT	Nucleic acid test
OMT	Oral mucosal transudate
PBMC	Peripheral blood mononuclear cell
PCR	Polymerase chain reaction
RT	Reverse transcriptase
WB	Western blot

I. Introduction

Technologic advances in HIV laboratory testing continue to aid in screening, diagnosis, and patient management. Effective methods for detection of HIV-related laboratory markers are critical for both accurate HIV screening and for monitoring patients for disease progression and viral resistance to therapy. This chapter provides an overview of currently available HIV laboratory screening methods, viral load assays, and HIV resistance tests. Many new technologies that will further enhance testing methods are in various stages of development.

Patients presenting for testing within 36 hours of exposure to HIV should be assessed for post-exposure prophylaxis (see Post-Exposure Prophylaxis Guidelines). Expert advice may be obtained from the National Clinicians' Consultation Center PEP Line at 1-888-HIV-4911 (1-888-448-4911).

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This article was provided by New York State Department of Health AIDS Institute.