Risk score can help predict which people living with HIV have highest risk of kidney disease during tenofovir treatment

Michael Carter
Published: 31 March 2014

Investigators in the United States have developed a risk score to predict which people living with HIV have the highest risk of developing chronic kidney disease. Published in the online edition of AIDS, the risk score is based on the Framingham score used to predict cardiovascular disease risk. The investigators hope their score will help doctors and the people in their care to reach decisions about the use of anti-HIV drugs associated with kidney dysfunction.

Kidney disease is a recognised complication of untreated HIV infection. Certain antiretroviral drugs have also been associated with an increased risk of kidney disease, especially combinations that include the drug tenofovir (Viread also in the combination pills Truvada, Atripla and Eviplera).

Tenofovir is a potent and well-tolerated drug recommended for first-line antiretroviral therapy around the world. To better guide the use of tenofovir, investigators from the US Department of Veterans Affairs sought to develop a scoring tool to predict the individualised five-year risk of chronic kidney disease (CKD) in people living with HIV.

The risk score was based on the records of 21,590 male patients who started HIV therapy between 1997 and 2010.

Chronic kidney disease was defined as estimated glomerular filtration rate (eGFR) below 60ml/min/1.73m2.

Older age, elevated glucose, elevated systolic blood pressure, hypertension, elevated triglycerides, proteinuria and a low CD4 cell count were all associated with the development of chronic kidney disease and included in the risk score.

During five-years of follow-up, 7.7% of the men taking tenofovir developed chronic kidney disease compared to 3.8% of men taking a combination which did not include tenofovir.

For both tenofovir- and non-tenofovir users there was a relationship between their risk scores and the development of chronic kidney disease.

For non-users, the absolute five-year risk increased from less than 1% for men with a zero risk score to 16% for men with risk scores of nine and above.

A similar relationship between risk score and absolute risk was observed in the men taking tenofovir. Individuals with a score of zero had a 1.4% five-year risk, increasing to a 21.4% for men with the highest risk scores.

Increasing duration of tenofovir use was associated with a higher five-year rate of chronic kidney disease (10.9% for those with over one year of use compared to 4.9% for men with less than one year of use). The increased risk associated with longer duration of tenofovir therapy was found across the range of risk scores.

The investigators used the case of a hypothetical 55-year-old man to illustrate the value of their model when reaching treatment decisions. The man was described as having a normal CD4 count and glucose, no proteinuria. However, he had high blood pressure, hypertension and elevated triglycerides. His total risk score was eight. If he was not taking tenofovir, he had an 11% chance of developing chronic kidney disease over five years; this increased to 19% with tenofovir use.

“Our scoring system allows risk assessment to be quantified, providing physicians and patients with an estimate of the absolute risk of developing CKD and providing a more nuanced algorithm for HIV treatment,” comment the authors. “Our CKD risk score could aid clinicians in designing first-line HIV treatment regimens optimized for safety as well as efficacy.”

Reference

Scherzer R et al. A chronic kidney disease risk score to determine tenofovir safety in a prospective cohort of HIV-positive male veterans. AIDS, online edition ahead of print. DOI:10.1097/QAD0000000000000258, 2014.