Tenofovir doesn't harm growth of kids' bones, suggests small study

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Treatment with tenofovir (Viread) does not affect the growth of children’s bones, according to a small Italian study published in the December 1st edition of the Journal of Acquired Immune Deficiency Syndromes.

Reductions in bone mineral density and bone mineral content have previously been seen in both adults and children treated with tenofovir, but the Italian investigators found that “twelve months of treatment with tenofovir at the indicated dose is not detrimental for bone mineral accrual in HIV-infected children.”

The study involved 16 HIV-positive children aged between six and 18 years of age. All switched from a stable antiretroviral treatment regimen consisting of 3TC (lamivudine, Epivir), d4T (stavudine, Zerit) and a protease inhibitor to a regimen consisting of 3TC, tenofovir and efavirenz (Sustiva). The treatment dose of tenofovir was dependent on body surface area.

Glossary

bone mineral density (BMD)

The higher your bone mineral content, the denser your bones are. And the denser your bones, the stronger they are and the less likely they are to break. A bone density test uses X-rays to measure how many grams of calcium and other bone minerals are packed into a segment of bone. The bones that are most commonly tested are in the spine, hip and sometimes the forearm. 

matched

In a case-control study, a process to make the cases and the controls comparable with respect to extraneous factors. For example, each case is matched individually with a control subject on variables such as age, sex and HIV status. 

sample size

A study has adequate statistical power if it can reliably detect a clinically important difference (i.e. between two treatments) if a difference actually exists. If a study is under-powered, there are not enough people taking part and the study may not tell us whether one treatment is better than the other.

sample

Studies aim to give information that will be applicable to a large group of people (e.g. adults with diagnosed HIV in the UK). Because it is impractical to conduct a study with such a large group, only a sub-group (a sample) takes part in a study. This isn’t a problem as long as the characteristics of the sample are similar to those of the wider group (e.g. in terms of age, gender, CD4 count and years since diagnosis).

dual energy x-ray absorptiometry scan (DXA or DEXA)

A test that uses low-dose x-rays to measure bone mineral density, including calcium content, in a section of bone. They are used to detect osteoporosis and predict the risk of bone fracture. 

All the children had experienced normal growth and sexual development. On entry to the study five were prepubescent, three were in mid-puberty and the remaining eight children were in late puberty.

Bone mineral content and bone mineral density were measured in the lumbar spine region and the whole skeleton using a DEXA scan twelve months before the treatment switch, at the time when treatment was changed, and twelve months later. The investigators calculated expected changes in bone mineral content and bone mineral density using 166 healthy controls. They then plotted changes in bone mineral content and density in the HIV-positive children against age-matched controls.

The 16 HIV-positive children remained well throughout the study period and all maintained a viral load below 50 copies/ml after the treatment switch. The investigators found that after the switch to tenofovir the children had increases in their bone mineral density and content which were not significantly different from those seen in the healthy age-matched controls.

“The current study shows that switching antiretroviral treatment to tenofovir does not impair bone mineral accrual in HIV-infected children”, write the investigators.

They suggest that their study may have produced different findings to earlier investigations involving children taking tenofovir because of the universal good health of individuals in their study.

However, the investigators concede, “the small sample size may be a limitation of this study and…that there is a need to confirm the bone safety of tenofovir in a larger number of HIV-infected children.”

References

Giacomet V et al. 1 12-month treatment with tenofovir does not impair bone mineral accrual in HIV-infected children. J Acquir Immune Defic Syndr 40: 448 – 450, 2005.