HIV TESTING STRATEGIES

Transcription

1 HIV TESTING STRATEGIES Ralph R. Frerichs, D.V.M., Dr.P.H. Pressor UCLA Department Epidemiology EPI 227, 11 am - Noon, May 1, Background on Testing Issues HIV Prevention Strategic Plan CDC Goal 2: Increased Knowledge Serostatus By 2, through voluntary counseling and testing, increase from the current estimated 7% to 9% the proportion HIV- people in the United States who know they are. 2 Source: CDC. HIV Prevention Strategic Plan through 2, February 3, 26. Est. Persons throughout the World Living with HIV/AIDS (in millions) Frerichs HIV Testing Controversy '8 '82 In a viewpoint, I recommended personal screening for HIV The Lancet 343, 96-62, 1994 '84 '86 '88 '9 '92 '94 '96 '98 ' '2 My intent remains to provide susceptibles with knowledge to avoid HIV infection and promote virus recognition among HIV persons. '4 '6 Controversies over HIV Testing Worldwide reluctance to test persons who might be harmed if found to be HIV positive homosexual men women intending to be married pregnant women Some feel that that benefit not testing exceeds the harm that may come from HIV testing the notion harm, however, does not usually include passing on the virus to a susceptible partner Year (19... and 2...) 3 6 1

2 Assigned Reading Public Health Implications unprotected anal intercourse sampling gay community venues in London anonymous behavioral questionnaire anonymous saliva samples 7 Source: Sex Transm Infect 8, , Homosexual Men Have homosexual men become more conscientious about avoiding transmission to susceptible partners? Pregnant Women Should pregnant women in high risk settings be required to ask for an HIV test (i.e., opt-in) or be routinely given an HIV test (i.e., opt-out)? Homosexual men who socialized in gay venues across London Who benefits from keeping HIV status unknown? Even with routine testing, there remains a large void in learning HIV status Source: Sex Transm Infect 8, , Source: MMWR 3(46), , Reported Unprotected Anal Intercourse with 1+ Partners in Past Year HIV Treatment with Anti-retroviral Drugs 1 About one-third had not know their HIV status 9 Reported Unprotected Anal Intercourse with 1+ Partners in Past Year (%) Previously tested and counseled, perhaps several times Who benefits from keeping HIV status secret? 1 Undiagnosed Diagnosed Source: Sex Transm Infect 8, , 24. Prior Diagnostic Status among HIV Saliva Positive Men 9 Who to treat and at what cost? 12 2

3 Estimated Global Coverage with Antiretroviral Therapy End 23 Need HIV testing before being able to find and treat asymptomatic HIV/AIDS 1. Infected blood Universal testing Blood Transfusion blood recipient Source: WHO. World Health Report, Test and avoid contaminated blood 16 HIV Infection in the United States in Years Gone By The group that transmits the disease Few if any Cures 4, incident cases per year 4, prevalent disease cases 4, deaths per year 1. Infected partner Occasional testing Monogamous anal sex for one year Following 1-12 years infection, the person with HIV dies. 4, prevalent carriers created 4, new infections each year 14 susceptible sexual partner Test and avoid or always use condom 17 Few if any permanent cures Current HIV Infection in the United States The group that transmits the disease 4, incident cases per year 1,, prevalent disease cases 13,68 deaths per year (23) (effective therapy) 1. Routine testing Pregnant Women If and unaware mother Following infection, persons remain alive due to effective therapy but still harbor the virus, serving as potential transmitters 1,, prevalent carriers create 4, new infections each year 1 child Tested, treated and no breastfeeding 18 3

4 Planned HIV Testing Strategy in the United States 1. Occasional testing Assay One Rapid Test < 2 min. Infected partner Monogamous vaginal sex for one year susceptible sexual partner Test and avoid or always use condom 19 Test + Test - Assay Two Negative Test + Test? Test - Positive* Indeterminate** Negative *If newly positive, confirm with another sample Western Blot **retest in two weeks High Specificity (few false positives) Potential transmitters 22 Test result Sensitivity = HIV+ HIV- B False positives D True negatives HIV- High sensitivity implies few false negatives A A + C HIV Testing HIV+ A True positives C False negatives Truth High specificity implies few false positives Specificity = D B + D 2 Personal Screening for HIV (now available in USA) Home Collection (with telephone counseling) Laboratory (3) (2) (4) Telephone counseling and referral 23 Usual HIV Testing Strategy in the United States Assay One ELISA Personal Screening for HIV (not yet available in USA) Home Collection (with no telephone counseling) (4) Laboratory Test + Test - Assay Two Negative Western Blot Test + Test? Test - Positive* Indeterminate** Negative Potential transmitters (2) (3) () *If newly positive, confirm with another sample **retest in two weeks High Specificity (few false positives) 21 No counseling, but informed with brochures and posters and by the general media 24 4

5 Personal Screening for HIV (not yet available in USA) Home Testing Conclusion Transmission Initial screening for HIV infection is done in the privacy the home Saliva strip or whole blood strip No counseling, but informed with brochures, posters and the general media Because the low infectivity (i.e., ability to lodge and multiply) HIV, transmission the virus should be easy to prevent, if infection status is known. Universal and continued condom use with at-risk partners is good in principal but appears to be too much to expect many people. HIV testing has been highly effective in preventing transfusionbased transmission and passage from mother to fspring. An individualize prevention strategy that relies on personal screening holds promise, but only if inexpensive rapid tests are made widely available Additional Information on Rapid Testing Conclusion Treatment HIV detection is a necessary first step before administering antiretroviral therapy Fear testing and therapy cost are two major deterrents increased HIV/AIDS treatments in the developing world An individualize detection and treatment strategy that relies on personal screening to identify and lead to treatment holds promise, but only if inexpensive rapid tests are made widely available The Safe Light Testing blood Providing therapy Offering condoms Sensitive counseling Deploring discrimination Testing mothers and children The difficult darkness widespread testing HIV reporting personal screening partner notification monogamy/abstinence 27