December 8, 2013
Medicine is a data-driven discipline and, as its practitioners, we are addicted to the metrics we have established as markers of disease. The hallmark of HIV infection is depletion of the CD4+ cell pool and so it goes that we track lymphocyte subsets -- worriedly, before we had effective antiretrovirals, and then triumphantly as these medications rolled out. However, the value of close CD4+ cell count monitoring is now questionable given that many clinics report that 80% - 90% of their patients have undetectable levels of HIV RNA and CD4+ cell counts plateau with long-term control of the virus. But addictions are hard to kick.
A report from Gale and colleagues from the Washington, D.C., Veteran's Affairs (VA) Medical Center may help us order CD4 cell+ counts less reflexively. Looking at 832 HIV-infected patients with a CD4+ cell count of 200 cells/mm3 and a suppressed viral load, the investigators found that CD4+ cell counts maintained above 200 cells/mm3 (when Pneumocystis pneumonia [PCP] prophylaxis would be indicated) in 93%. Most of the dips in CD4+ cell counts occurred in those with counts between 200 - 299 cells/mm3, with 24% of such patients having a drop below the 200 cells/mm3 threshold. In contrast, for those with an initial count of 300 cells/mm3, there was a greater than 99% likelihood that their counts would not fall to 200 cells/mm3 or less. The team took a stab at calculating the savings that would be had by reducing CD4+ cell count testing to annual for the 550 patients with suppressed virus and counts above 300 cells/mm3 in their cohort. Assuming the test cost $37.92, $41,000 would have been saved.
We order way too many CD4+ cell counts and it is time to dial this back. For patients with decent CD4+ cell counts (i.e., 300 cells/mm3 plus) and consistently undetectable viral loads without events that could be expected to drop cell counts (e.g., chemotherapy), there is no need to bird-dog lymphocyte subsets. The savings in cost are not inconsequential and one can even argue the ethics of repeat testing that the data suggest will be of little to no value for the vast majority of those tested.
Even if these data convince us, it will likely take more to reassure our patients, who we have trained to obsessively follow their counts. We need to explain the rationale clearly. In doing so, we can also impart to our patients the message that their HIV is in a type of remission maintained with medication without the need for adding another dot to extend the flat line of their counts. Most will understand, especially those who actually have to pay some or all of their laboratory bills.
What are some other top clinical developments of 2013? Read more of Dr. Wohl's picks.
David Alain Wohl, M.D., is an associate professor of medicine in the Division of Infectious Diseases at the University of North Carolina and site leader of the University of North Carolina AIDS Clinical Trials Unit at Chapel Hill.
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