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A New Case Definition for HIV Infection

May 5, 2014

A New Case Definition for HIV Infection

  1. Abigail Zuger, MD

Changes based on the newest testing strategies affect patients of all ages.

  1. Abigail Zuger, MD

The surveillance case definitions for HIV infection and AIDS have been a work in progress for the last 30 years, as revisions keep pace with scientific advances. The newest revision combines case definitions for infants, children, and adults into a single document, incorporates new HIV-testing strategies, and aims to eliminate some of the ambiguity of past iterations. Two changes are most relevant to clinical practitioners:

1. The laboratory criteria for confirming HIV infection have been expanded to incorporate the newer testing algorithms that diverge from the usual enzyme-linked immunosorbent assay/Western blot sequence. For all adults, all children aged ≥18 months, and all younger children not at risk for perinatal infection, confirmed infection requires two positive immunologic tests that are “orthogonal,” using different antigens or principles. Acceptable combinations include an antigen/antibody test followed by an antibody-only test, an antibody test followed by a viral load assay, and a rapid antibody test followed by a conventional immunoassay (a positive Western blot is no longer required for diagnosis). A single positive result from a nonantibody test (p24 antigen, viral culture, viral load, or genotype) is also diagnostic.

2. The staging of HIV infection has been augmented by the addition of “stage 0” to indicate a very early infection diagnosed when standard markers are converting from negative to positive. The formal criteria specify a negative or indeterminate antibody, antigen/antibody, or nucleic acid test occurring within 6 months before a positive test of any type, or a positive test for HIV-specific viral markers occurring within 6 months of a negative or indeterminate antibody test. Criteria for stage 0 supersede and are independent of the criteria for other stages (which rely, as before, on CD4-cell counts and diagnosis of opportunistic illness). This new stage is particularly intended for patients with transiently low CD4-cell counts right after infection who in the past might have mistakenly been staged with advanced disease.

Other changes spell out up-to-date criteria for assigning “infected,” “uninfected,” and “indeterminate” status to children aged <18 months with perinatal HIV exposure and criteria for defining HIV-2 infection.

Comment

The case definitions here are used more by epidemiologists than by clinicians but are always helpful for teaching purposes. This update — the first since 2008 — does yeoman's work integrating a complex network into a more coherent whole.

  • Disclosures for Abigail Zuger, MD at time of publication Editorial boards Journal Watch AIDS Clinical Care; Clinical Infectious Diseases Other New York Times medical writer

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Reader Comments (1)

Sara Vazquez MD Physician

ICD 10 coding is going to require stage and specific diagnosis.

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