High rate of false-positive fourth-generation HIV tests seen in Texas cancer patients

Physicians should be aware of a high rate of false-positive fourth-generation HIV tests among cancer patients, especially among older women on plant alkaloid treatment, as reported by researchers in Texas.

About This Study

“False-Reactive Fourth-Generation Human Immunodeficiency Virus Testing in Cancer Patients” was published online on Nov. 1, 2023, in Clinical Infectious Diseases. The lead author is Chia-Yu Chiu of the Department of Infectious Diseases at the University of Texas Health Science Center at Houston, and of the Department of Infectious Diseases, Infection Control, and Employee Health at the University of Texas MD Anderson Cancer Center, also in in Houston.

Key Research Findings

This retrospective study of 43,637 cancer patients tested for HIV at a single center between 2016 and 2023 investigated false positive results when a fourth-generation antibody/antigen HIV test was used. The 272 cancer patients who tested positive for HIV were mostly white men (54% white, 69% men), and 39% of these participants were > 60 years old. Forty-six percent of the 111 participants on cancer treatment received plant alkaloids.

Confirmatory testing revealed that 29% of initial HIV tests were incorrect. While testing results did not affect cancer treatment, mental distress from the tests results was common. False-positive HIV tests were more common among older or female participants, and in participants treated with plant alkaloids (paclitaxel, docetaxel, vinblastine, and vincristine). Conversely, being Black or Brown, or co-infected with syphilis was associated with a reduced likelihood of a false-positive test.

Discussion Highlights and Implications for Practice

Study limitations reported included the lack of information on signal-to-cutoff ratios, which may impact false-positive rates, and the fact that cancer treatment usually included more than one medication, making it difficult to determine whether certain cancer therapies interacted with the HIV immunoassay.

The researchers pointed out that while other studies have found higher false-positive HIV test results in people infected with SARS-CoV-2, the current study did not show that association, possibly due to a small sample size. Clinicians should be aware of the high false-positive HIV testing rate among people with cancer and counsel their patients, especially those at low risk for HIV infection, accordingly, study authors recommended.

By Barbara Jungwirth