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Kidney signal trouble worsens over 5 years in Japanese on tenofovir

Mark Mascolini, IAS newsletter

Estimated glomerular filtration rate (eGFR), a signal of kidney function, declined steadily over 5 years in HIV positive Japanese taking tenofovir (TDF) compared with those taking abacavir. The TDF group did worse than the abacavir group by three eGFR measures.



The risk TDF poses to kidney function is well appreciated. But the long-term renal impact of TDF in people who continue taking this antiretroviral is not well understood. Typically, providers switch patients from TDF to another drug if their kidney function worsens.

To assess the long-term effects of TDF on kidney function in HIV-positive people, especially those with low body weight, Japanese researchers conducted this 5-year study of 422 antiretroviral-naive people who started a TDF regimen and 370 who started an abacavir regimen. All patients received care at a single center in Tokyo. People with lower weight are more vulnerable to TDF kidney toxicity.

The research team used logistic regression analysis to assess three renal endpoints: (1) decline in eGFR greater than 10 mL/min relative to the baseline measure, (2) more than 25% decline in eGFR, and (3) eGFR lower than 60 mL/min in two measures at least 3 months apart.

The study group had a median weight of 63 kg. Taking TDF rather than abacavir at least doubled chances of reaching all three endpoints, at the following adjusted odds ratios (aOR) and 95% confidence intervals (CI):

  • More than 10 mL/min drop in eGFR: aOR 2.1, 95% CI 1.45 to 3.14, p<0.001
  • More than 25% eGFR drop: aOR 2.1, 95% CI 1.50 to 2.90, p<0.001
  • Two eGFRs below 60 mL/min: aOR 3.9, 95% CI 1.62 to 9.36, p=0.002

Compared with the abacavir group, the average decline in eGFR grew larger as years taking TDF increased: −3.8 mL/min at 1 year, −3.6 mL/min at 2 years, −5.5 mL/min at 3 years, −6.6 mL/min at 4 years, and −10.3 mL/min at 5 years.

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In this cohort of patients with low body weight,” the authors conclude, “TDF exposure increased the risk of renal dysfunction” and “loss in eGFR relative to the control increased continuously up to 5 years.”

These findings should be interpreted cautiously because patients were not randomised to TDF or abacavir. As a result, factors not adjusted for when calculating odds ratios may have affected outcomes.

Source:
Mascolini M. Kidney signal trouble worsens over 5 years in Japanese on tenofovir. International AIDS Society online news report. (02 September 2014).
http://www.iasociety.org/Default.aspx?pageId=5&elementId=15988

Reference:

Nishijima T et al. Long-term exposure to tenofovir continuously decreases renal function in HIV-1-infected patients with low body weight: results from 10 years of follow-up. AIDS. 2014; 28: 1903-1910.
http://journals.lww.com/aidsonline/Abstract/2014/08240/Long_term_exposure_to_tenofovir_continuously.7.aspx

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