Category: Bone Densitometry or Body Composition

31 - Tracking of spine BMD (Bone Mineral Density) in infants exposed to TDF (tenofovir disproxil fumarate) medication in utero and/or during breast feeding

Background: Tracking bone mineral density (BMD) over time can is useful to monitor bone development in growing bones. Dual-energy X-ray absorptiometry (DXA) is an ideal method for children because of its low radiation dose. However, movement during scans is a problem.

The purpose of this analysis was to test whether other vertebrae combinations could be used as a surrogate to L1-L4 total BMD to assess the rate of change.

We used longitudinal observational data from IMPAACT P1084s: The Bone and Kidney Heath Substudy of the IMPAACT 1077 PROMISE Protocol. During recruitment period (August of 2011 to February of 2015) each participant received multiple DXA scans including lumbar spine at baseline (BL, 0-21 days of age) and at follow up (FU, 26 weeks). Participants were scanned using either the Hologic Discovery/Wi or Discovery/W systems (Hologic Inc., Marlborough, Massachusetts), and centrally analyzed using Apex 3.4 software. Two-sided Student T-test was used to observe the statistically significant difference in rate of change between L1-L4 referent total BMD and individual or combinations of vertebrae, and further validated with 2-fold cross validation. A clinically-significant change of 2% difference was also used.

Of the 750 participants, only 529 infants (325 girls and 204 boys) had valid BL and follow-up spine scans. The mean age was 15.9 ± 9.5 days for BL and 186.7 ± 15.3 days for FU visit. Standardized weight and length was 3.49 ± 2.53kg & 49.84 ± 6.13cm for BL and 7.48 ± 3.25kg & 65.48 ± 26.30cm for FU. The mean total spine BMD rate of change was 16.85 ± 17.72 % per 6 months. Statistically insignificant differences were seen for L1/L4, L2/L3, and L2/L3/L4 BMD combinations compared to L1-L4. Only one additional region was statistically different but not clinically, L1L3L4.

The rates of change for four vertebral combinations shows similar rates of change did not differ from changes in L1-L4 spine BMD. Although the regions validated, further investigations are underway to determine the causal reasons for these specific combinations. A following up study in healthy volunteer sample group (same age and sex) may be of interest to rule out any possible effects of TDF exposure in utero and during breast-feeding.

Bo Fan

San Francisco, California

Kathleen George

Clinical Research Specialist
FHI 360
Durham, North Carolina

John Shepherd

Adjunct Professor
San Francisco, California

Professor John Shepherd is a Professor in the Department of Radiology and the Director of the Body Composition, Exercise Physiology, and Energy Metabolism Lab at the University of California, San Francisco. He is a Fulbright fellow to the Karolinska Institute in Stockholm, and the current President of the International Society for Clinical Densitometry. He is an expert in quantitative breast imaging as well as musculoskeletal imaging using X-ray absorptiometry techniques. Dr. Shepherd received his BS in Engineering Physics from Texas Tech University and his PhD in Engineering Physics from the University of Virginia followed by a postdoctoral fellowship in Biophysics at Princeton University. He is also a Certified Clinical Densitometrist.

Dr. Shepherd’s research interests involve quantitative imaging methods for tissue composition using X-rays. He is the PI for the Shape Up! Study to examine 3D optical whole body scans in 1500 indivuduals from 5 to 85 years, and the PI of the 3CB study to extend mammography to measure the composition of invasive lesions. He has been the DXA CORE director for NHANES study since 1999. His current research interests include shape and appearance modeling and deep learning methods to big imaging datasets including DXA bone denisty scans. He has published over 150 peer reviewed articles in these fields.

Markus Sommer

Assistant CRC
San Francisco, California

Lynda Stranix-Chibanda

University of Zimbabwe
Harare, Not Applicable, Zimbabwe

Leila Kazemi

Program Manager
San Francisco, California