Screening of HIV infection: role of molecular and immunological assays

Abstract

Due to technical improvements and new developments of immunological assays, the reliability of serological laboratory diagnosis of HIV infection has improved considerably and the residual risk, due to the diagnostic window for transfusion-transmitted HIV, has been reduced significantly. Through the addition of nucleic acid amplification tests (NAT) to blood donor screening, the residual risk can de further decreased by up to 50%, depending on the sensitivity of the NAT protocol and whether individual or pooled blood donations are screened. In-house and commercially available NAT have been implemented in blood banks as HIV only or multiplexed HIV and hepatitis B or C virus assays. As an alternative to separate antigen and antibody screening, combined fourth-generation assays have been developed in 1997, and have achieved a high degree of sensitivity and specificity. Thus, they can replace stand-alone antigen and third-generation antibody assays. While they are used in the routine diagnostics of HIV infection in many countries throughout the world, they probably represent no alternative for NAT in blood-donor screening in industrialized countries. In the next few years, technical improvements will further simplify NAT screening. While there is still some potential to improve the detection threshold of NAT, the sensitivity of the antigen module of fourth-generation assays (a lowest concentration of 3-5 pg of p24 antigen) is probably very close to its technical limit.

False-Positive Rate of a “Fourth-Generation” HIV Antigen/Antibody Combination Assay in an Area of Low HIV Prevalence

“…Currently, these new fourth-generation assays are widely used for routine laboratory diagnosis of HIV. Assay specificity is another important point to consider, and Weber determined the specificity of fourth-generation HIV assays launched after 2001 to be between 99.50% and 99.90% (6). Our study using the Architect HIV Combo assay showed comparable results (specificity, 99.78%; 95% CI, 99.75% to 99.80%).…”

New Automated Chemiluminescence Immunoassay for Simultaneous but Separate Detection of Human Immunodeficiency Virus Antigens and Antibodies

“…Over the last few decades, considerable efforts have been made to narrow the window period for detection of HIV (2). Although antibody (Ab) tests (third-generation assays) have been developed to reduce this period, they are not able to identify patients with acute HIV infection who have not yet produced specific antibodies.…”

Infecciones de transmisión sexual silentes: la muestra de orina permite una adecuada detección

“…La técnica de ELISA utilizada en el tamizaje de VIH, ha experimentado numerosos cambios, ya que en el año 1985 se utilizaba lisado vírico como base antigénica, logrando detectar los anticuerpos 40 días después de la infección 45 . En el año 1987 el lisado fue sustituido por proteínas recombinantes y péptidos sintéticos, aumentando la sensibilidad y detectando la presencia de anticuerpos 33-35 días luego de la infección 46 . En el año 1994 la técnica ELISA adquirió el formato sandwich, logrando detectar anticuerpos IgG e IgM y reducir el período de detección a 22 días 46 .…”

“…En el año 1987 el lisado fue sustituido por proteínas recombinantes y péptidos sintéticos, aumentando la sensibilidad y detectando la presencia de anticuerpos 33-35 días luego de la infección 46 . En el año 1994 la técnica ELISA adquirió el formato sandwich, logrando detectar anticuerpos IgG e IgM y reducir el período de detección a 22 días 46 . Actualmente, se utilizan técnicas que posibilitan la detección simultánea de anticuerpo y el antígeno p24, reduciendo el período de detección a aproximadamente 13-15 días, alcanzando un porcentaje de sensibilidad de 99,9% 45 .…”