Federal Effort to Control HIV Depends on Increasing Testing, Treatment Adherence

To control its spread in the U.S., HIV infection must be diagnosed early and persons with HIV infection must be quickly linked to sustained care and treatment. These are the core tenets of the Trump Administration's proposed 10-year initiative, Ending the HIV Epidemic – A Plan for America. However, knowing one's status, linking newly diagnosed patients to care and maintaining treatment adherence pose barriers to curtailing the HIV epidemic.

Too Much Transmission, Too Little Testing

“Providers should screen patients for HIV infection at least once and test some patients more frequently; rapidly link, engage, or re-engage patients into comprehensive HIV care; and encourage patients to sustain viral suppression for their own health and because of the tremendous prevention benefits,” write the authors of a recently released Vital Signs, HIV Transmission Along the Continuum of Care, published in the March 18 Morbidity and Mortality Weekly Report.

According to the U.S. Centers for Disease Control and Prevention (CDC), everyone aged 13 to 64 years should be tested at least once; those at higher risk for HIV should be tested at least annually. Sexually active gay and bisexual men need even more frequent testing — every 3 to 6 months. Unfortunately, real-world testing rates fall far below these guidelines and not knowing one’s HIV status contributes to ongoing transmission.

In the Vital Signs, CDC released findings of its update to the Progression and Transmission of HIV (PATH 2.0) model to estimate 2016 U.S. transmission rates by step along the HIV care continuum. The CDC researchers found that in 2016, approximately 80 percent of new infections occurred due to persons with HIV infection who did not know they were infected and persons with diagnosed HIV infection who were not in care. More than one-third of transmissions (38 percent) occurred among the 15 percent of people living with HIV who were unaware of their status. In all, CDC estimates that approximately 165,000 Americans live with HIV, but do not know they have it.

Stopping Transmission Among Those in Care

The CDC findings show that 20 percent of new infections occur from the 11 percent of persons with HIV infection who are in care but not virally suppressed. In addition to maintaining viral suppression to prevent sexual transmission to partners, pre-exposure prophylaxis (PrEP), a daily regimen of two oral antiretroviral drugs in a single pill, has proven to be highly effective in preventing HIV infection for individuals at high risk. While known to be effective, many patients are not compliant with the PrEP regimen.

At the Conference on Retroviruses and Opportunistic Infections (Seattle, Wash.; March 4-7) researchers presented early data on a novel point-of-care (POC) antibody-based assay that can assess patients’ adherence to treatment. Real-time, POC detection of non-adherence can permit immediate intervention by providers to optimize PrEP outcomes.

Matthew Spinelli, M.D., from University of California, San Francisco, and colleagues measured urine tenofovir (TFV) levels using this novel antibody-based assay and compared TFV levels to detection levels using the gold standard liquid chromatography tandem mass spectrometry (LC-MS/MS) of hair and dried blood spot (DBS) samples among 125 men and transwomen participating in a PrEP demonstration trial.

They found that urine TFV levels were significantly correlated with other pharmacologic measures with high specificity in detecting sub-optimal dosing (low adherence). The median urinary TFV level by the immunoassay was 15,000 ng/ml (in those who remained HIV-negative), 5,500 in 11 individuals who eventually seroconverted, and undetectable (less than 1,000 ng/ml) in all nine individuals at the time of seroconversion.

"What we found is low versus high levels of TFV with this amino acid test were associated with 14-fold higher risk of developing HIV in the future. The idea is that if we have this adherence information at the bedside through the means of a POC test we can intervene and help support our patients and prevent HIV infections Spinelli told MedPage Today at the conference. "Because PrEP is a prevention intervention, it's not like a lot of other diseases … where I have sort of a surrogate marker of how people are doing, like A1C in diabetes or the viral load in HIV."

Spinelli says the goal of this POC test would be to have more information about patients' adherence to have that conversation with them at the visit and support them and motivate them to have good adherence on PrEP to stay HIV negative.

Takeaway: Testing will play an important role in a federal push to curtail the spread of HIV in the United States by increasing HIV screening and through possible future adoption of POC tests able to detect PrEP adherence.

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This article originally appeared in G2 Intelligence, Diagnostic Testing & Emerging Technologies, May 2019