August 7, 2008
Turner Overton, M.D.
In this analysis, we looked at the baseline kidney function of our patients based on the simplified MDRD [Modification of Diet in Renal Disease] equation to determine the prevalence of renal insufficiency, and then looked at parameters that were associated with that.
We found that about 40% of our cohort has stage 2 or worse kidney function, and that means they have a GFR [glomerular filtration rate] of less than 90 mL/min/1.73 m2. The vast majority of these are stage 2, in that they have a GFR between 60 and 90 mL/min/1.73 m2.
We subsequently looked at renal insufficiency. The factors that were predictive of a low GFR were greater weight, the presence of albumen in the urine, higher cystatin C, the diagnosis of hypertension, the concomitant use of tenofovir [TDF, Viread] and ritonavir [RTV, Norvir], and white race.
What we are interested in moving forward with next is looking at the longitudinal data from our cohort to see what the changes are over time and to see if some of these predictors are consistent longitudinally.
Could you tell me a little bit about the patient characteristics?
Absolutely. The SUN Study is really representative of the current HAART [highly active antiretroviral therapy] era. The study name "SUN" stands for the Study to Understand the Natural History of HIV/AIDS in the Era of Effective Therapy.
The mean patient age is about 41 years. One fourth of our patients are women. Thirty percent are African American and 10% are Hispanic. The vast majority (80%) are on antiretroviral therapy, with about 80% of those having a viral load that's undetectable.
Tell me a little bit about the characteristics by renal function. Did you see the problems more in black or Hispanic patients?
Interestingly, we actually found more renal problems in the white race than in African Americans, which is a little different than some other [study] populations.2,3 That's why we're interested in the longitudinal data, because we believe that these patients have been infected longer and are more likely to have had an opportunistic infection, as well as a longer duration of their HIV infection.
What does this mean in terms of tenofovir use? Is this a warning sign?
I think we're all very worried about tenofovir. We did find that tenofovir use was associated with lower renal function, so it is an issue. I think the key right now is for us to get some longitudinal data to see what the effect is in that direction. I think it's critical that -- regardless of whether your patient is on tenofovir or some other agent -- you make sure you're monitoring renal function over time, and address any changes, particularly if someone is developing significant renal insufficiency.
This transcript has been lightly edited for clarity.
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