Laboratory tests used in diagnosis and treatment of AIDS

Detailed knowledge of the structure of the human immunodeficiency virus (HIV) triggered a rapid development of methods for diagnosing the infection. The enzyme-linked immunoadsorbent assay (ELISA) determining the presence of antibodies to the protein components of the virus in toto is highly sensitive and provides thus the basic screening approach. It is however somewhat less specific and therefore all positive results are verified by the Western blot method which detects individual HIV proteins and possesses a 99.9% specificity. In sporadic cases the latent period between HIV infection and the possibility to establish antibody response may extend to six months and even longer. The polymerase chain reaction (PCR) revealing the presence of DNA HIV in infected cells is suitable for detecting these seronegative patients. It is also the method of choice in diagnosing HIV infection in children of infected mothers since HIV antibodies are in newborns mostly of maternal origin. HIV antibodies, particularly the antigen p 24, can be quantified in serum by using ELISA. As their amounts correlate with the severity of the disease determination of antigen p 24 concentration is an indicator of the therapeutic efficacy of preparations such as AZT. The recently developed quantitative PCR is a further potentially valuable method for assessing the therapeutic effect since treatment should reduce the amount of cellular HIV DNA. With the exception of testing the sensitivity of HIV strains to antiretrovirus preparations, HIV cultures are rarely set up since they are technically demanding and involve a considerable risk.