New definition of kidney disease for clinical trials could lead to new treatments

Chronic kidney disease (CKD) is a worldwide public health problem that affects 26 million Americans in the U.S., with 600,000 requiring dialysis or kidney transplantation. Despite its prevalence, there are fewer clinical trials for kidney disease than any other common disease. In December 2012, the National Kidney Foundation (NKF) and the Food and Drug Administration (FDA), challenged the research community to evaluate the current definition of kidney disease progression and examine whether improvements were possible. At that time, NFK and FDA officials viewed favorably emerging evidence that a decline in estimated kidney function was promising as a reliable indicator of kidney disease progression. This research grew directly out of the NFK-FDA challenge.

For the study, a global Chronic Kidney Disease Prognosis Consortium led by Josef Coresh, MD, PhD, MHS, a professor at the Bloomberg School, analyzed data from 1.7 million participants recruited into 35 cohorts in dozens of countries from 1975-2011 and followed for an average of 5 years. The researchers' points of comparison were the FDA's current definition of CKD disease onset for clinical trials -- a doubling of serum creatinine, a blood marker that assesses kidney function -- and the emerging evidence on a decline in estimated kidney function.

Researchers first analyzed kidney disease progression among all participants during a baseline period of two years. They then examined how this progression predicted subsequent disease progression to the observed 12,344 cases of end-stage renal diseases (ESRD) and 223,944 deaths. The study found that the current serum-creatinine standard used in clinical trials which is associated with a 57% reduction in kidney function carried very high risk -- a 32-fold increased risk of ESRD and 3.7-fold increased risk of mortality but only occurred in less than 1% of participants in the two-year baseline period.

In contrast, a 30% decline in kidney function, also measured by serum creatinine levels, occurred in 7% of participants in the two-year baseline period. This was associated with a 5-fold higher risk of end-stage renal disease (ESRD) and 1.8-fold higher risk of mortality. This level of risk is high and yet common and early enough to facilitate testing if new therapies are working.

"Chronic kidney disease is often asymptomatic until it's too late," notes Dr. Coresh. "This new definition will help standardize following patients to determine when their disease progresses significantly enough to elevate risk. This will assist in patient care, research studies and development of new therapies."