HIV DNA and antibodies in syringes from injecting drug users: a comparison of detection techniques

Direct HIV testing of individual injecting drug users is not always feasible. As an alternative, we have evaluated the sensitivity and specificity of several techniques for detecting HIV-1-specific products in used syringes.

Polymerase chain reaction (PCR) and antibody-capture assays were compared using syringes prepared with blood from HIV-1-positive and -negative individuals.

PCR sensitivity was maximized, enabling detection of single copies of HIV-1-specific proviral DNA. The limits of detection from used syringes were determined for PCR by diluting extracts and correlated to CD4+ cell counts. Similarly, limits of detection were determined for enzyme immunoassays (EIA) and Western blot.

All techniques were highly specific, although with PCR false-positives were detected occasionally. EIA proved more sensitive than Western blot in detecting needles containing HIV-1-infected individuals' blood. Even after prolonged storage of syringes at room temperature, EIA was equal to or better than PCR as an HIV-1 detection technique. The most sensitive method for detecting HIV-1 was the viral-based EIA when the recommended predilution step was omitted.

EIA proved preferable to PCR because of their higher sensitivity, absence of false-positives and easier sample preparation and analysis.