A Phase 4 study is to characterize the profile of low bone mineral density (BMD) in ≥ 50 year old male subjects and post-menopausal female subjects on any tenofovir disoproxil fumarate (TDF)-based regimen

Inclusion Criteria:

• Must have the ability to understand and sign a written informed consent form, which must be obtained prior to initiation of any study procedures.

• HIV-1 infected subjects regardless of race or ethnicity

• Use of one of the following taken as a stable, continuous, NRTI-containing antiretroviral (ARV) regimen for ≥ 3 years are allowed (within-class change of agents other than TDF within 3 years of study entry are permitted as specified):

  • TDF plus PI/r-containing regimen including subjects who switched from one TDF plus PI/r regimen to another TDF plus PI/r regimen
  • a TDF plus non-PI/r-containing regimen including subjects who switched from one TDF plus non-PI/r regimen to another TDF plus non-PI/r regimen
  • a Non-TDF NRTI plus a PI/r-containing regimen including subjects who switched from one non-TDF NRTI plus PI/r regimen to another non-TDF NRTI regimen plus PI/r regimen
  • a Non-TDF NRTI plus a non-PI/r-containing regimen including subjects who switched from one non-TDF NRTI plus non-PI/r regimen to another non-TDF NRTI regimen plus non-PI/r regimen

• Of note, subjects in the non-TDF groups must have never taken a regimen that includes TDF (including previous exposure to TDF for pre-exposure prophylaxis (PrEP))

• Subjects included in the TDF groups must have always taken a regimen that includes TDF. Non-PI/r agents include non-nucleoside reverse transcriptase inhibitors (NNRTIs), integrase inhibitors, triple nucleoside inhibitors and non-boosted protease inhibitors

• Male subjects must be ≥ 50 years of age

• Female subjects must be postmenopausal. Menopause can be assumed to have occurred in a woman when there is either appropriate medical documentation of prior complete bilateral oophorectomy or permanent cessation of previously occurring menses > 12 months as a result of ovarian failure or bilateral oophorectomy with documentation of hormonal deficiency by a certified healthcare provided

• Adequate records available to evaluate medical history for the 3 years prior to study entry

Exclusion Criteria:

• Subject has a contraindication to dual-energy X-ray absorptiometry (DEXA) scans
• Subject has a history of osteoporosis before initiating Highly Active Antiretroviral Treatment (HAART)

Study population of ≥ 50 year old male subjects and post-menopausal female subjects