Inside the “black box” of the antibody test: deconstructing the official classification of “risk” in test algorithms used for identifying the Human Immunodeficiency Virus

This paper interrogates the last 20 years in the British experience of using official antibody test algorithms to detect the human immunodeficiency virus (HIV). Case definitions of the Acquired Immunodeficiency Syndrome (AIDS) cite antibody test methodologies licensed since 1985 for screening purposes and derived from laboratory identification of HIV. Two common (yet surrogate) methodologies are the enzyme-linked immunosorbent assay (ELISA) and the Western blot (WB), both used for screening human populations. Test manufacturers publicise the interpretative flexibility of these tests, which may produce false or indeterminate results, given laboratory identification of HIV is cited as problematic, time-intensive and as using surrogate techniques. Globally, public health officials publish differing algorithms for testing of human subjects. The paper shows how these algorithms (whilst aiming to balance test specificity/sensitivity), are based on perceptions of ‘risk’ of exposure determined during pre-test dialogue: how the test subject is positioned as ‘high’/‘low’ risk and within a hierarchy of exposure categories. The interpretation of indeterminate results is problematic given the possibility of false results, which are ruled out by estimating the risk of exposure (‘window period’) and the seroprevalence in the population of the test subject. It is argued that during the last 20 years experience with these test algorithms the interpretation of the test ‘result’ is not wholly ‘objective’ or laboratory-determined, as it relies as much upon the classification of the test subject as being ‘at risk’ during pre-test dialogue as it does upon the “epidemo logic” of the ELISA or WB, data which often remains ‘black-boxed’ from a critical public scrutiny. Using data from tested subjects and published accounts/texts, the paper deconstructs the classification of ‘risk’ embodied by official test algorithms and analyses how the ambiguity/uncertainty characteristic of antibody-test methodologies have sociological implications for ethical decision-making, self-identity and social movements.