Surveillance Case Definitions for HIV Infection and AIDS Revised
Laurie Barclay, MD
Medscape Medical News 2008. © 2008 Medscape
December 10, 2008 — Surveillance case definitions have been revised for HIV infection in adults, adolescents, and children younger than 18 months of age and for HIV infection and AIDS in children aged 18 months to younger than 13 years, according to a report published in the December 5 issue of the Morbidity & Mortality Weekly Report. These case definitions are intended for public health surveillance only and not as a guide for clinical diagnosis.
"Since the beginning of the [HIV] epidemic, case definitions for HIV infection and [AIDS] have undergone several revisions to respond to diagnostic and therapeutic advances and to improve standardization and comparability of surveillance data regarding persons at all stages of HIV disease," write Eileen Schneider, MD, and colleagues from the Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention. "HIV testing is now widely available, and diagnostic testing has continued to improve; these changes are reflected in the 2008 revised case definition for HIV infection, which now requires laboratory-confirmed evidence of HIV infection to meet the case definition among adults, adolescents, and children aged 18 months to <13 years."
Specific revisions are as follows:
For adults and adolescents aged older than 13 years, the HIV infection and AIDS classification system and surveillance case definitions have been revised and combined into a single case definition for HIV infection.
The surveillance case definition in this group requires laboratory-confirmed evidence of HIV infection. The stage of infection is determined from the lowest CD4+ T-lymphocyte count (or concordant CD4+ T-lymphocyte percentage of total lymphocytes) or from the presence of AIDS-defining conditions.
When the CD4+ T-lymphocyte count and the CD4+ T-lymphocyte percentage do not correspond to the same severity stage, the case should be classified as the more severe stage.
Acute HIV infection, which occurs approximately during the time from viral acquisition until seroconversion, is diagnosed from documented, detectable HIV RNA or DNA or p24 antigen in plasma or serum when HIV antibody test on the same day is negative or indeterminate.
Laboratory criteria for HIV infection are:
A positive result from an HIV antibody screening test (eg, reactive enzyme immunoassay) confirmed by a positive result from a supplemental HIV antibody test (eg, Western blot or indirect immunofluorescence assay); or
A positive result or report of a detectable quantity from any of the following HIV virologic tests: HIV DNA or RNA detection test (eg, polymerase chain reaction); HIV p24 antigen test, including neutralization assay; or HIV isolation (viral culture).
Case classification for HIV infection stages is as follows:
Stage 1: No AIDS-defining condition, and either CD4+ T-lymphocyte count greater than 500 cells/μL or CD4+ T-lymphocyte percentage of total lymphocytes higher than 29%.
Stage 2: No AIDS-defining condition and either CD4+ T-lymphocyte count of 200 to 499 cells/μL or CD4+ T-lymphocyte percentage of total lymphocytes of 14% to 28%.
Stage 3 (AIDS): Laboratory confirmation of HIV infection and CD4+ T-lymphocyte count of more than 200 cells/μL or CD4+ T-lymphocyte percentage of more than 14%, or documentation of an AIDS-defining condition (with laboratory confirmation of HIV infection).
Stage unknown: Laboratory confirmation of HIV infection and absent data on CD4+ T-lymphocyte count or percentage and absent information on presence of AIDS-defining conditions.
For children younger than 13 years, the HIV infection case definition has been revised.
For children younger than 18 months, the HIV infection case definition replaces the definition published in 1999 and applies to all HIV variants. It takes into account newly available testing technologies.
Laboratory criteria for children younger than 18 months have been revised for the category of presumptively uninfected with HIV, but no significant changes have been made to the other 3 categories (definitively HIV infected, presumptively HIV infected, and definitively uninfected with HIV).
For surveillance purposes, a child younger than 18 months who is born to an HIV-infected mother is categorized as presumptively uninfected with HIV if the criteria for definitively uninfected with HIV are not met, if there is no other laboratory or clinical evidence of HIV infection, and if at least 1 of the following laboratory criteria are met:
2 negative RNA or DNA virologic tests, from separate specimens, both of which were obtained at age older than 2 weeks and 1 of which was obtained at age older than 4 weeks; or
1 negative RNA or a DNA virologic test from a specimen obtained at age older than 8 weeks; or
1 negative HIV antibody test from a specimen obtained at age older than 6 months; or
1 positive HIV virologic test followed by 2 or more negative tests from separate specimens, 1 of which is a virologic test from a specimen obtained at age older than 8 weeks or an HIV antibody test from a specimen obtained at age older than 6 months.
For children aged 18 months to younger than 13 years, laboratory-confirmed evidence of HIV infection is now required to meet the surveillance case definition for HIV infection. Without such evidence, diagnostic confirmation of an AIDS-defining condition alone is no longer sufficient to classify a child as HIV infected for surveillance purposes.
For children aged 18 months to younger than 13 years, the AIDS case definition has been revised and now requires laboratory-confirmed evidence of HIV infection.
For children younger than 18 months, there have been no changes to the AIDS case definition.
For children younger than 13 years, there have been no changes to the HIV infection classification system or to the 24 AIDS-defining conditions.
"Public health surveillance data are used primarily for monitoring the HIV epidemic and for planning on a population level, not for making clinical decisions for individual patients," the authors write. "[The Centers for Disease Control and Prevention] and the Council of State and Territorial Epidemiologists recommend that all states and territories conduct case surveillance of HIV infection and AIDS using the 2008 surveillance case definitions, effective immediately."
Morb Mortal Wkly Rep. 2008;57(RR10);1—8.
