October 27, 2008
There's nothing like hearing the results of studies directly from those who actually conducted the research. In this interview, you'll meet one of these impressive HIV researchers and read her explanation of the study she presented at ICAAC/IDSA 2008.
My name is Birgit Grund. I am from the University of Minnesota's Coordinating Centers for Biometric Research. I'm a statistician on the SMART study,1 specifically the body composition substudy of SMART.2 In this substudy, X-ray scans were used to measure different measures of body composition, including bone marrow density. We had longitudinal measurements of spine bone marrow density by quantitative computed tomography [QCT], which measures the inside of the bone (the trabecular bone); spine bone marrow density by DEXA [dual-energy X-ray absorptiometry], which measures mostly cortical bone, but also trabecular bone; and bone marrow density by DEXA at the hip. So we have three major bone marrow density locations.
Birgit Grund, Ph.D.
Could you talk a little bit about the differences?
Differences at the hip between the two study arms were 1.4% off baseline [P = .002]. Differences at the spine, spine QCT, were 2.9% [P = .01]. Differences by DEXA in the spine were 1.2% [P = .05]. Average follow-up was about two years. Of that, time spent off antiretroviral therapy was a little bit over a year in the intermittent therapy arm.
Is there any take-home for clinicians back home?
I think further research needs to be done. It's too early to speak about recommendations, but it certainly prompts us to think about guidelines for HIV-infected patients.
Was there anything in the patient characteristics that would be connected to this decrease in bone density?
Twenty-three percent were women. The average age of participants was 44 years. About a quarter of participants were black. A little less than half were white.
Could it be a function of age at all?
Well, it is known that bone marrow density decreases with age, but the decrease is not as high as we have seen it here in this study. It's a little bit higher than what you would expect in the HIV-uninfected population of that age. However, it is known that in cross-sectional studies, persons with HIV tend to have somewhat lower bone marrow density than persons who are not HIV infected.
Thank you very much.
This transcript has been lightly edited for clarity.