Tests performed daily, Urgent samples result available in 12 - 20 hours (if negative).
Confirmation testing weekly (Western Blot).
Positive results are telephoned through to the requesting doctor.
Testing is using Roche Laboratories ECL method on COBAS e602 / e801 modules
Human immunodeficiency virus is classified as a primate lentivirus, family Retroviridae. Most human infection is human immunodeficiency virus type 1 (HIV 1) and less commonly a related virus HIV 2, prevalent in West Africa.
HIV integrates into the target cell (usually T-helper CD4+ lymphocytes) genome as a provirus and the viral genome is copied during cell replication resulting in the carriage of the virus for life.
HIV has been isolated from numerous body fluids but only blood, semen, cervical secretions and breast milk have been implicated epidemiologically in the transmission of disease. Accepted modes of transmission are sexual, percutaneous, parenteral, vertical and through breastfeeding.
Initially, HIV infection manifests itself as an acute infection in the majority of individuals with symptoms including fever and lymphadenopathy. Severity is variable with a duration in the order of 1-2 weeks. The second stage of infection is termed the asymptomatic stage and in 50% of individuals will last for over 10 years.
Following the asymptomatic stage, the advanced HIV disease phase usually lasts 1-2 years and is characterised by profound immune dysfunction and increased susceptibility to opportunistic infections. Until the advent of effective therapy infection was ultimately lethal.
WB provides a profile of antibodies to HIV. This enables confirmation of specific reactivity to the entire range of HIV antigens.
There are three predominant features of WB banding that relate to the stage of HIV infection :
(a) In early seroconversion, the high molecular weight envelope glycoproteins (gp160/120) and core peptide bands will be reactive.
(b) During the asymptomatic phase of the illness, full viral banding is expected.
(c) During late stage HIV infection, anti-p24 levels decline, which relates to a liberation of HIV in vast numbers from CD4 lymphocytes.
Current EIA incorporates p24antigen, thus enabling detection of HIV infection during the viraemic phase and before antibody has developed. WB is less sensitive than the screening EIA so low level EIA reactors may be negative on WB. A second blood sample should be tested 3 weeks later.
For further information contact the laboratory (contact via Lablink: 22000 or (09) 307-8995 or 0800 522 7587) ,or:
the Virology team
virology@adhb.govt.nz