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  17th European AIDS Conference
November 6-9
2019, Basel
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Comparison of changes in bone microarchitecture with abacavir-lamivudine versus tenofovir disoproxil fumarate-emtricitabine in adults living with HIV Greater BMD Decline With TDF Than ABC, But Similar Drop in Trabecular Bone Score
  17th European AIDS Conference, November 6-9, 2019, Basel
Mark Mascolini
Trabecular bone score, a measure of bone microarchitecture that can be derived from DXA scans [1], declined by similar amounts in antiretroviral-naive people who took first-line tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) or abacavir/lamivudine (ABC/3TC) for 48 weeks, even though declines in bone mineral density (BMD) were significantly greater with TDF/FTC [2]. Veterans Administration (VA) and University of Texas (UT) researchers who conducted this study proposed that trabecular bone score "could potentially increase the accuracy of fracture risk assessment with newer antiretrovirals."
BMD considers the density of bone but not the microarchitecture apparent in trabecular (porous) bone. Research links low trabecular bone score to history of fracture and new fracture risk "largely independent of BMD" and FRAX [1]. Trabecular bone score can be calculated from standard DXA scans. Analysis of 201 people with HIV and 262 without HIV found that those with HIV had lower trabecular bone scores independent of lumbar spine BMD [3]. Higher smoking rates, higher bone turnover, and treatment with protease inhibitors--but not TDF--contributed to lower trabecular bone scores in the HIV group.
The VA/UT study focused on antiretroviral-naive adults randomized to a regimen containing TDF/FTC or ABC/3TC (both with efavirenz) in the European ASSERT trial [4]. To calculate trabecular bone score and BMD, the investigators used DXA images created at study weeks 0, 24, and 48. They used mixed-effects repeated-measures models to compare changes in trabecular bone score between treatment arms in analyses controlling for baseline values, age, body mass index, race, and sex.
The analysis included 75 people randomized to TDF/FTC and 83 assigned to ABC/3TC. The TDF and ABC groups were similar in proportions of men (76% and 75%), proportions of whites (73% and 76%) and blacks (20% and 17%), age (average 41 and 39), and initial BMD and trabecular bone score (1.32 and 1.33).
At study weeks 24 and 48, adjusted analyses determined that lumbar spine BMD declined more with TDF than ABC (-2.6% versus -1.7%, and -2.2% and -1.4%). Trabecular bone score dropped significantly with both TDF and ABC at weeks 24 (-1.4% and -1.8%) and 48 (-2.3% and -1.5%), and these differences between groups were not statistically significant (P = 0.3).
Age and body mass index predicted BMD (P < 0.05) but not trabecular bone score. A higher initial trabecular bone score predicted a greater drop in that score in people taking TDF but not ABC (P < 0.01). In the combined TDF and ABC groups, change in trabecular bone score correlated with change in BMD at week 24 (r = 0.18, P = 0.03) and week 48 (r = 0.41, P < 0.01).
The researchers concluded that first-line therapy with TDF/FTC or ABC/3TC (both with efavirenz) led to significant drops in trabecular bone score, indicating weakening bone microarchitecture, but small differences between the two groups were not statistically significant. They proposed that trabecular bone score could improve fracture prediction in people taking antiretroviral therapy.
1. Shevroja E, Lamy O, Kohlmeier L, Koromani F, Rivadeneira F, Hans D. Use of trabecular bone score (TBS) as a complementary approach to dual-energy x-ray absorptiometry (DXA) for fracture risk assessment in clinical practice. J Clin Densitom. 2017;20:334-345.
2. Bedimo B, Huet B, Nguyen V, Moore-Matthews D, Poindexter J, Maalouf NM. Comparison of changes in bone microarchitecture with abacavir-lamivudine versus tenofovir disoproxil fumarate-emtricitabine in adults living with HIV. 17th European AIDS Conference, November 6-9, G2019, Basel. Abstract PE9/8.
3. McGinty T, Cotter AG, Sabin CA, et al. Assessment of trabecular bone score, an index of bone microarchitecture, in HIV positive and HIV negative persons within the HIV UPBEAT cohort. PLoS One. 2019;14:e0213440.
4. Moyle GJ, Stellbrink HJ, Compston J, et al. 96-Week results of abacavir/lamivudine versus tenofovir/emtricitabine, plus efavirenz, in antiretroviral-naive, HIV-1-infected adults: ASSERT study. Antivir Ther. 2013;18:905-913.
Comparison of Changes in Bone Microarchitecture with Abacavir-Lamivudine versus Tenofovir Disoproxil Fumarate-Emtricitabine in Adults Living with HIV
R. Bedimo1,2, B. Huet2, V. Nguyen1, D. Moore-Matthews1, J.P. Poindexter2, N.M. Maalouf2
1VA North Texas Health Care System, Dallas, TX, 2University of Texas Southwestern Medical Center, Dallas, TX