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HIV Epidemiology


HIV Epidemiology

Contact Information
Los Angeles County
Department of Public Health
HIV Epidemiology, DHSP                       600 S. Commonwealth Ave. Suite 1920
Los Angeles, CA 90005
Phone: (213) 351-8196
Fax: (213) 487-9386


        LAC's ZIP code level data/maps on HIV

HIV Epidemiology - Interview-Based Case-Control Study Among Patients Attending Publicly Funded STD Clinics

In March of 1994, the HIV Epidemiology Program initiated the Record-Based Incidence Study (RBIS) study in four public STD clinics in Los Angeles County. This prospective record-based HIV seroincidence study involves the routine abstraction of medical record information, including HIV test results, for all STD patients who receive a confidential HIV test. Through the RBIS medical records database, HIV test results are linked to one another whenever an STD patient has more than one confidential HIV test resulting from repeat STD visits.

While the seroincidence data obtained through the RBIS are vital to the timely projection of the course of the HIV epidemic, such data are limited. For example, these data cannot provide detailed risk behavior information that are not routinely collected for treatment purposes. Additionally, follow-up information from record-based studies is unequally spaced and cannot provide consistent information about time-specific exposures. Without time-specific exposure information we are not able to evaluate the precise relationship between behaviors and the risk of newly acquired HIV infection. Such information is urgently needed for the development of prevention programs that specifically target those at greatest risk of acquiring or transmitting HIV.

A nested case-control study conducted within the existing record-based incidence study is an efficient and valid way of addressing risk exposure questions that remain unanswered in this high- risk population.


  1. To identify newly acquired HIV infections among STD clinic attendees who receive more than one confidential HIV test.
  2. To assess behavioral etiologic factors associated with HIV seroconversion in an STD population.
  3. To assess the biologic and genetic variation of the human immunodeficiency virus among recent seroconverters.

Study Design:

The Interview-Based Case-Control study (IBCC) is a nested case-control design that compares behavioral and socio-demographic risk factors of HIV seroconverters identified in the RBIS with a minimum of three and a maximum of five controls who have two or more HIV-negative results documented in their medical record. Both cases and controls have at least two confidential HIV antibody tests recorded on their medical records on or after January 1, 1993. Cases have received one or more prior negative HIV tests and a subsequent positive HIV test during the study period. A maximum of five controls are selected and matched to each index case on clinic, gender, and date of the case's positive HIV test. Controls are eligible if a negative HIV test result is recorded within six months of the date of the case's positive HIV test.

Contact Persons:

Trista Bingham, M.P.H.

Shannon Hanrahan, M.A.
Research Analyst

View --->STD fact sheet

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