RETROVIRIDAE GENUS ONCOVIRUS HTLV1 and HTLV2 SPUMAVIRUS LENTIVIRUS

RETROVIRIDAE GENUS: ONCOVIRUS: HTLV-1 and HTLV-2 SPUMAVIRUS LENTIVIRUS: HIV-1 and HIV-2

NATURAL HISTORY Infection Asymptomatic Simptomatic AIDS 10 -7 Seroconversion 10 -6 1000 10 -5 Anti-HIV 10 -4 500 HIV RNA in plasma 10 -3 10 -2 10 -1 0 4 - 8 Weeks > 12 Years 2 - 3 Years HIV viral load # copies/ml T CD 4 count cels/ml CD 4

LABORATORY METHODS Screening tests: ELISA Agglutination Dot ELISA Ab’s + Ag p 24 (Dual tests) Rapid tests Confirmatory tests: Western blot Immunofluorescence RIPA Monitoring tests: Viral Load CD 4 count tests Perinatal Diagnosis: PCR Ig. A Western blot Other tests: HIV Subtypes: ELISA, HMA HIV Genotyping assays PCR HIV-2, ELISA HIV-2

WHO/UNAIDS STRATEGIES Test objective Prevalence Strategy Transfusion/Transplant All I Epidemiological Surveillance > 10% < 10 % I II Symptomatic > 30% Diagnosis < 30% I II Asymptomatic > 10% < 10% II III

WHO/UNAIDS STRATEGIES OBJECTIVE HIV TESTING STRATEGY Reducing Western Blot use Screening test combinations Choose a strategy based on: *Analysis objective *Sensibility and Specificity *HIV Prevalence

FUNCTIONS OF HIV TESTING Screening blood for transfusions Surveillance and monitoring Voluntary counseling and testing Perinatal prevention programs

TRADITIONAL DIAGNOSTIC HIV TESTING Sinception, testing technology driven by blood needs: High blood volume Equipment (specific) Technically demanding Centralized, time-consuming

NEW SIMPLE DIAGNOSIS RAPID ASSAYS Point of service testing Minimal equipment requeriments Straightforward interpretation Immediate test results Low cost

¿ WHAT RAPID TESTS ARE? They are screening tests for HIV antibody detection that produce results very fast (5 to 30 min)

RAPID TESTS 1) Agglutination tests Principle of the test: They use gelatine perticles coated with HIV antigens, neutralized. These particles in the presence of antibodies, form an agglutination net. They was developed for use with serum or plasma.

PRUEBAS RAPIDAS (Aglutinación de Partículas)

RAPID TESTS 2) Immunodot Principle of the test: They are a enzymatic immune assay (EIA) based on specific Ab detection for HIV-1 and HIV-2 with antigens in 2 reaction sites.

RAPID TESTS (IMMUNODOT)

RAPID TESTS 3) Immunochromatography (lateral flow tests) Principle of the test: If the samples contain antibodies against HIV-1 and/or HIV-2, these antibodies will bind to viral antigens coated onto a membrane. The Ag-Ab complex will be visible : blue line on the test

RAPID TESTS Immunocromatography Positive Negative Invalid test

RAPID TESTS (SAMPLE) Serum / plasma Whole blood Oral fluid (crevicular)

CONSIDERATIONS Annually are carried out a large number of screening tests Most of them are performed for the first time Many people do not return for their results There is many rapid test available. Most of them with unknown performance

EFFECT OF PREVALENCE According to test specificity HIV Prevalence Predictive Value Positive 10 % 5% 3% 2% 1% 0. 5 % 0. 3 % 0. 1 % 96 % 91 % 86 % 80 % 67 % 50 % 38 % 18 %

LESSONS LEARNED Both client and staff prefer same-day result. Immediate counseling can be provided Combination-test algorithms yield accurate results Same-day results help clients to receive immediate referrals and services they need

EPIDEMIOLOGY IN MEXICO REPORTED CASES AND ESTIMATE OF PLWHIV June 30 2008 Reported cases 121, 718 PLWHIV 200, 000 Perinatal cases 22 New cases 1, 767 Source: http: www. salud. gob. mx/conasida In order to prevent newborn HIV infections one million of pregnant women are tested using rapid tests

CONCLUSIONS Rapid HIV tests are essential for early access to prevention, care and support services Rapid testing and quality counseling is feasible and can help staff to provide immediate care and support Numerous accurate rapid tests exist It is necessary evaluate the performance of the test in our countries

PERSONAL

rvazquez@salud. gob. mx rvzqzroberto@yahoo. com