HIV testing

Although the status of some HIV-infected patients admitted to the ICU will be known and declared, in the majority it will not ( Table 2).

Kttwflfc ftfflmg KirtlCU lBT Hin fi^Stal :ew<H

i.ifrieitv iCUbvr berate tf preiena- aJ opfcfeg OWiW »rttrJJ

t/iLfcfft»: tf patenriCU 'earn :« juMri _js re rsi iKWt Iff HIV rtHtnyi rt W Mfl tpjfi & rtWWBMh

Table 2 Status of HIV-infected patients admitted to the ICU

In some patients the possibility of underlying HIV infection will emerge with the acquisition of the knowledge that the patient belongs to an at-risk group (e.g. intravenous drug user) or from information conveyed to the ICU team by the patient's friends, relatives, or partner(s); in others the discovery of physical signs (e.g. oral candidiasis or cytomegalovirus retinitis, or pathology such as Cryptococcus neoformans meningitis and fungemia, disseminated Mycobacterium tuberculosis, or Kaposi's sarcoma) will prompt the diagnosis.

A conscious patient should not be tested for HIV unless patient counseling occurs and there are facilities available for post-test counseling in the event of a positive result. In the United States consent is required. Unconscious patients or those sedated and mechanically ventilated are clearly unable to give consent for HIV testing, and in the United States consent comes from the next of kin. The need for testing in this situation is rare, for example if organ donation is being considered ( Miller et al 1993).

Before performing an HIV test it is important to consider the natural history of HIV infection in order to interpret the result, particularly as an 'HIV test' is often mistakenly called an 'AIDS test' and it is frequently incorrectly stated that a negative 'HIV test' result excludes HIV infection. It is also important that the physician requesting the test poses the question: 'Will a negative or positive HIV test result influence management of the patient?' Following exposure to HIV, through sex, shared needles, or receipt of contaminated blood, antibodies to HIV develop in most patients within 6 months. In the majority antibodies develop within 6 weeks; however, in some cases there is a delay of up to 12 months, and a few patients never develop antibodies. During this window time between exposure and development of antibodies (so-called seroconversion), patients are infected with HIV, they are infectious, and HIV antigen and DNA are detectable in peripheral blood, yet they are HIV negative on testing as the HIV test detects only antibodies to HIV and not the virus itself.

Other patients, in whom HIV infection has been documented by a previous positive HIV test result, lose their HIV antibodies as their disease progresses and the CD4 lymphocyte count falls. They are also infected with HIV and are infectious, yet they are negative on routine HIV testing. Another small group of patients, despite being infected with HIV and having detectable HIV antigen and DNA in peripheral blood, never develop antibodies and yet may have AIDS-defining illnesses such as P. carinii pneumonia and low CD4 lymphocyte counts with negative HIV test results.

The HIV test is based on detection of antibodies, most often by an antibody capture-enzyme-linked immunosorbent assay (ELISA). A positive result is always confirmed by other laboratory tests on the same sample using different methods to detect HIV antibodies (e.g. particle agglutination assays and Western blotting) and by repeating the HIV antibody detection tests on a second sample of blood.

In the clinical situation where an HIV test is negative but HIV infection is suspected on clinical grounds (e.g. cerebral toxoplasma abscess) or where it is imperative that HIV infection is excluded (e.g. in a patient being worked up for organ transplantation), more refined tests should be carried out for HIV genome detection by polymerase chain reaction or HIV p24 or RT antigen detection.

Healthy Fat Loss For A Longer Life

Healthy Fat Loss For A Longer Life

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