Old habits die hard. Since the 1980s, when we first came to understand that CD4 cell depletion is one of the hallmarks of immune deficiency in persons with AIDS, we clinicians have checked the CD4 counts of our stable patients every 3 months (more often for those who were sick or starting new therapy). Our patients (and we) worried from visit to visit whether their CD4 counts (we called them T-cells then) rose or dropped (mostly they dropped), and our spirits rose and fell with their counts.
That was then. Today we have highly effective antiretroviral treatment for human immunodeficiency virus (HIV) and a much better marker of how our patients are doing: the HIV viral load. Patients with undetectable virus in their blood are likely to do well as long as they keep taking their medication. The first sign of trouble is an elevated viral load. If perchance a patient of mine had a major drop in the CD4 count despite having an undetectable viral load, my first thought would be that the CD4 count was in error.
So, if CD4 counts are no longer driving treatment decisions in stable patients who are virally suppressed while receiving antiretroviral treatment, why do we still order these tests? Because it is our habit, and our patients expect it. Although ordering the test likely causes little harm to our patients (unnecessary anxiety if there is a false-negative drop in the count), the tests are expensive. As demonstrated by Hyle et al, if we would order them at most yearly for our stable virally suppressed patients (instead of every 6 months), we would save $10 million a year in the United States. We could use that money in ways that would likely have a much greater impact on the population of HIV-infected persons, including early HIV detection and linkage to medical care, medication adherence counseling (so that CD4 counts do not drop owing to missed doses), substance abuse treatment, and supportive housing.
Resources are finite. We should always seek to spend them in ways that bring the greatest good. Eliminating unnecessary CD4 counts and providing treatment with more impact is a good way to start.
Disclaimer: The views expressed herein are those of the author and not necessarily the views of the County of Los Angeles, California.
Katz MH. Directing Resources to Where They Are the Most Needed. JAMA Intern Med. 2013;173(18):1748. doi:10.1001/jamainternmed.2013.8590