This case report adds HIV vaccination to the list of well-known causes of false-positive results in HIV antibody–screening tests and illustrates the problems often associated with the interpretation of WBs. Timely and effective means of confirming HIV screening tests have become increasingly important as more centers integrate HIV screening into routine clinical care as recommended by the CDC.
In many laboratory settings, NATs for HIV-1 RNA are more widely available and less costly than WB and are not subject to indeterminate results. Although quantitative HIV-1 NATs have not been cleared by the US Food and Drug Administration (FDA) for diagnosis, they have been used for years for evaluating patients thought to be acutely infected. These patients typically have high viral loads ranging from 105 to 106 copies/mL, and the results present no problems with interpretation. The reports of false-positive results in viral load tests all occurred with a single method (Versant bDNA test; Siemens Healthcare Diagnostics); results were <104 copies/mL.
The APTIMA HIV-1 RNA Qualitative Assay (Gen-Probe), currently the only NAT that has been FDA-cleared for diagnosis of infection, can be used to diagnose neonatal and acute infections, confirm positive results in antibody-screening tests, and resolve indeterminate WB results. As the authors point out, a NAT was the next step in the diagnostic work-up, but it was deferred when the vaccination history was obtained.
The rare individuals who are infected with HIV-1 but who progress to AIDS either very slowly or not at all pose another diagnostic dilemma. In these long-term nonprogressors, HIV-1 antibody is easily demonstrated, but these individuals show low or undetectable HIV-1 RNA loads in the assays available to clinical laboratories. Viremic controllers have low but readily measurable virus loads. Elite controllers suppress HIV to extremely low concentrations, which are measurable only with the most analytically sensitive laboratory techniques.
Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.
Authors' Disclosures of Potential Conflicts of Interest: Upon manuscript submission, all authors completed the Disclosures of Potential Conflict of Interest form. Potential conflicts of interest:
Employment or Leadership: None declared.
Consultant or Advisory Role: F.S. Nolte, Gen-Probe and Abbott Molecular.
Stock Ownership: None declared.
Honoraria: None declared.
Research Funding: None declared.
Expert Testimony: None declared.
Role of Sponsor: The funding organizations played no role in the design of study, choice of enrolled patients, review and interpretation of data, or preparation or approval of manuscript.
- Received for publication July 23, 2010.
- Accepted for publication August 2, 2010.
- © 2010 The American Association for Clinical Chemistry