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New Viral Load Technologies: Potential for a Real-Time Virologic Mess

July 7, 2011

Bethsheba Johnson, G.N.P.-B.C., A.A.H.I.V.S.

Bethsheba Johnson, G.N.P.-B.C., A.A.H.I.V.S., is an associate medical director of St. Hope Foundation in Houston, Texas.

A while back, after a challenging day in the office, I came home to the pleasure of reading the Winter 2011 edition of HIV Specialist, the magazine of the American Academy of HIV Medicine (AAHIVM). Of particular interest to my weary brain was an article by Bruce J. Packett II entitled "The Evolution of Viral Load Technologies."

Well, I have to say: He woke me up with his research and comments. This article discussed the measurement of viral load using real-time PCR technology, and how a small survey of AAHIVM providers (N = 233) felt about the recent advances in viral load testing technology.

Having been in the field of HIV far longer than a minute, I have watched the ability of each new generation of viral load assays to detect and quantify lower levels of the virus: less than 400 copies/mL, then 75, then 50, then 48, and now the current lowest, 20.

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We have told our patients that one of the goals of HIV antiretroviral therapy is to reduce the viral load to the lowest level possible. In other words, the goal is to get to "undetectable." "Undetectable" simply means to have HIV viral suppression less than the assay's lowest level of detection and quantification. In some labs, that is less than 20 copies/mL. But what happens when the lowest level of quantification (LLQ) changes for a patient that has been previously undetectable? If a patient has a viral load of 30, but it had previously been measured with an assay that has an LLQ of less than 48 copies/mL, and now it is being measured with an assay that has an LLQ of less than 20, is that patient now "failing" therapy?

I've noticed that this can be a problematic question. I recently sat in a speaker's bureau training (by an unnamed pharmaceutical company), and quite a few of the participants did not know what low-level viremia meant to the management of the client.

The current U.S. Department of Health and Human Services (DHHS) Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents, on the topic of monitoring viral load, states that depending on the assay used, it is not far-fetched to have "isolated viral blips" typically less than 400 copies/mL present themselves in successfully treated patients. These blips are not thought to represent virologic failure or ongoing replication.

Meanwhile, as we have discussed in our practice, low-level viremia (less than 200 copies/mL) without evidence of virologic failure appears to be more common with some viral load assays than others. As our clinic is part of the AIDS Clinical Trials Group (ACTG), we define virologic failure as a confirmed viral load greater than 200 copies/mL -- but individual providers outside of the ACTG had differing opinions on that threshold. In fact, even within our practice there are differences between health care providers in how to interpret this information. One provider said he considered virologic failure to be at 1,000 copies/mL confirmed.

The DHHS guidelines give the following definitions:

  • Virologic suppression: A confirmed HIV RNA level below the limit of assay detection (e.g., <48 copies/mL).
  • Virologic failure: The inability to achieve or maintain suppression of viral replication (to an HIV RNA level <200 copies/mL).
  • Incomplete virologic response: Two consecutive plasma HIV RNA levels >200 copies/mL after 24 weeks on an antiretroviral regimen. Baseline HIV RNA may affect the time course of response, and some regimens will take longer than others to suppress HIV RNA levels.
  • Virologic rebound: Confirmed detectable HIV RNA (to >200 copies/mL) after virologic suppression.
  • Persistent low-level viremia: Confirmed detectable HIV RNA levels that are <1,000 copies/mL.
  • Virologic blip: After virologic suppression, an isolated detectable HIV RNA level that is followed by a return to virologic suppression.

So now back to my patient with a viral load of 30 who had previously been "undetectable." Is it considered low-level viremia? Should we be concerned as health care providers? Should the patient be concerned?

Most patients will become anxious and not understand that changing the LLQ can in fact change whether we call them "undetectable" or "low-level viremic." Using the previous example of a viral load of 30 or 40 copies/mL, I've had several patients in the last year look at me with a blank stare after I gave them their results. The first question the patient asks is, "But is that still undetectable?"

Well, technically, the answer is no, you are not considered undetectable, because the LLQ has changed. So now the patient becomes even more anxious.

Hopefully, a conversation will ensue at this point that assures the patient there is no cause for alarm; that they are not failing the regimen and all of their wonderful adherence is still working. A case could be made that that 30 or 40 has been their viral load all along, but the test could not quantify such low levels until now.

Conversely, a viral load of greater than 200 copies/mL confirmed could possibly indicate virologic failure if the patient has been shown to be adherent. But can it also be a virologic blip?

In his article, Mr. Packett suggests that health care providers need more education on the new real-time PCR technologies. I agree with you wholeheartedly, Mr. Packett.

Stay tuned for HIV and aging, as well as other potential-hot-mess issues, in my future posts!

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