Tracking the subtle kidney damage that can lead to chronic kidney disease in HIV patients is increasingly important as people survive longer and may have an increased risk of renal dysfunction as a result of their disease, therapy-related damage, or co-morbid conditions such as diabetes mellitus and hypertension.
Researchers have reported on a potentially more sensitive marker for the early detection of renal impairment than the marker currently considered the standard. Results were reported during the 12th Conference on Retroviruses and Opportunistic Infections (CROI).
In an observational study involving 1,625 patients from the CHORUS Cohort, five times more patients were identified as having stage 3 kidney disease by estimating glomerular filtration rate (GFR) rather than testing for the traditional marker, serum creatinine (sCr) levels. The two markers detected a comparable number of patients with stage 4 chronic kidney disease.
"The National Kidney Foundation has stated that GFR is the best overall indicator of kidney function, especially in patients with co-morbid conditions, and recently indicated that the use of serum creatinine alone may not be suitable for the detection of renal impairment," said Stephen L. Becker, M.D., Pacific Horizon Medical Group, San Francisco, who presented the study. Because 24 hour urines were not collected in the CHORUS Cohort, GFRs were estimated.
"More than 10 percent of our patients had renal dysfunction using the GFR Stage 3+ criterion, a level defined by the National Kidney Foundation as chronic kidney disease," Dr. Becker said. Only about 2 percent of Grade 1+ sCr elevations would have been identified using sCr alone.
Of 20 clinical events related to renal insufficiency observed in the study population, 45 percent were predicted based on sCr levels alone, compared to 95 percent predicted by GFR.
Elevation in the level of creatinine is a marker of kidney function. Estimated GFR takes into account sCr levels, but also considers other variables such as age, race and sex that affect sCr.
Overall, the elevations in sCr observed in CHORUS were consistent with those seen in other populations, and the proportion of patients with extreme Stage 4+ GFR values was comparable to results seen for Grade 4+ sCr in other studies.
"HIV positive people are living longer as advances continue to be made in treatment and more drug options are available. The challenge now is to keep people healthy and to detect early on if a particular factor might be causing damage," said Doug Manion, M.D., vice president for HIV Clinical Research for the Infectious Diseases Medicines Development Center (MDC), GlaxoSmithKline. "This study suggests that estimated GFR may be a more sensitive marker that will help healthcare providers detect and treat kidney problems earlier than with sCr alone," he said. Further study of renal function in patients treated with a wide range of antiretroviral agents is planned for the future.
CHORUS (Collaborations in HIV Outcomes Research - U.S.) is an observational research database initiated in 1997 and with an enrollment of more than 8,000 patients in 7 study sites. It is a longitudinal study that collects data in the course of regular medical care and through periodic questionnaires.
CHORUS is funded by GlaxoSmithKline, but is overseen by an independent scientific board of physicians and other HIV experts.
GlaxoSmithKline is one of the world's leading research-based pharmaceutical and healthcare companies and an industry leader in HIV research and therapies. GSK is a leader in the development of fixed dose combination products. The company is engaged in basic research programs designed to investigate new targets to treat HIV.