PCR-testi HIV:lle alle 4 viikkoa tartunnasta

Nestistä löydettyjen tekstien perusteella PCR testi antaa vastauksen 95% luotettavuudella noin 22 päivän kuluttua tartunnasta.

- PCR-testi pitää varmentaa sekä negatiivisen testituloksen että positiivisen testituloksen jälkeen, ottamalla tavallinen vasta-aine testi 3 kk kohdalla. Jos saat selvän positiivisen PCR:stä, voit olla melko verma että saat sen myös vastaaineteitistä. Jos saat negatiivisen PCR:stä, voit olla melko varma että saat sen myös vastaainetestistä.

- Älä ota anti-retrovirus lääkkeitä ennekuin menet PCR testiin koska niiden käyttö voi johtaa väärään negatiiviseen tulokseen.

- Väärä positiivinen voi johtua mm laboratorio virheestä kun muutama mikrogramma vierasta saastunutta verta näytteessäsi/laitteistossa riittää antamaan väärän positiivisen. Testaa siis positiivinen vielä 3 kk kohdalla vastaaine testilla.

- Väärä negatiivinen voi johtua siitä että HIV:ta oli veressäsi liian vähän, mutta useimmilla on jo parin viikon päästä tartunnasta tarpeeksi HIV:tä veressään. Lähestulkoon kaikkilla (99%) on tarpeeksi HIV:tä veressää 4 viikon jälkeen.

http://www.labsafe.com/lab-tests/test/436?utm_source=sli&utm_medium=cpc&wcw=sli

In addition to the general HIV Antibody screening test, the HIV Proviral DNA test is also run. If a test result is positive, then confirmatory testing with Western Blot analysis is performed to ensure accuracy. The sophisticated HIV Proviral DNA test has been found to be 99.9% accurate in detecting the presence of HIV at 28 or more days after infection. It can be used to detect HIV before seroconversion, and therefore is very valuable in determining the course of treatment, if necessary. It can be used earlier to detect HIV but the accuracy before 28 days is not known.

Detecting AHI (Acute HIV infection) with nucleic acid testing

The mode of detection of AHI displaying the most promise for a low prevalence area like
Wisconsin is nucleic acid testing (NAT) with polymerase chain reaction (PCR). PCR is a
molecular biological technique that enzymatically replicates and exponentially amplifies DNA
(or RNA using reverse transcriptase PCR). By using species-specific primers, nucleic acid from a
chosen biological agent, such as HIV-1, can be selectively amplified and detected to verify the
presence of the agent. Viral RNA and proviral DNA are abundantly present in the serum of an
acutely infected individual and can therefore be used for the diagnosis of AHI. Among the
attributes of NAT with PCR are its high levels of specificity and sensitivity and its drastic
reduction of the pre-diagnostic window period.

In October 2006, the FDA approved Gen-Probe’s APTIMA HIV-1 RNA Qualitative Assay for the
diagnosis of AHI. All other PCR-based HIV assays are approved for monitoring viral load to
manage care or to screen donated blood and tissue. The federal Centers for Disease Control and
Prevention revised recommendations for HIV testing of adults and adolescents suggests that,
where AHI is a possibility, a plasma RNA test should be used in conjunction with an HIV
antibody test to detect AHI.15 Beyond viral load tracking and blood and tissue screening, PCRbased
HIV assays have proven to be critically important in identifying HIV infection in
newborns of HIV positive mothers, due to the infants lacking antibody response.
PCR detection of HIV-1 nucleic acid is often used as the gold standard by which other testing
methods are compared.16,17,18 With sensitivities of NAT with PCR averaging 50 RNA copies per
mL, and peak viremia during acute infection ranging anywhere from 1,000 to 1,000,000 copies
per mL, detection of HIV infection at set point is highly predictive and confirmed.
The length of the pre-diagnostic window is a function of when a person becomes viremic. Kahn
estimates that initial viremia occurs as early as 3 days or as late as 11 days after infection.[15]
[b]Other studies indicate that detection with PCR can shorten the pre-diagnostic window period to
11 days[/b]. [1,19,20] With the window of detection ranging anywhere from 3 to 11 days post infection,
NAT with PCR can significantly improve detection of AHI over that of conventional antibody
testing.

http://www.dhfs.state.wi.us/aids-hiv/Update/Summer2007.pdf