An increase in the levels of serum phosphorus in African-American patients with a diagnosis of chronic kidney disease (CKD) is linked with a faster progression to kidney failure, also called end-stage renal disease (ESRD). These data, presented during the ASN Kidney Week 2015 (Nov. 3–8) in San Diego, California, corroborate previous results in Caucasian populations in the U.S.

Chronic kidney disease (CKD) refers to any condition that causes reduced kidney function over a period of time. CKD is present when a patient’s glomerular filtration rate remains below 60 milliliters per minute for more than three months, or when a patient’s urine albumin-to-creatinine ratio is over 30 milligrams of albumin for each gram of creatinine (30 mg/g). End-stage renal disease (ESRD) refers to total and permanent kidney failure. When the kidneys fail, the body retains fluids and harmful wastes build up. A person with ESRD needs treatment to replace the work of the failed kidneys.

Evidence has shown that African-Americans are over three times more likely to progress to kidney failure as Caucasians, and account for 32% of individuals suffering with ESRD. In the new study, a team of researchers from the Indiana University School of Medicine, led by Jonathan Bazeley, MD, wanted to determine if serum phosphorus, which has been found in previous studies in Caucasian populations to be associated with unfavorable clinical outcomes in patients with CKD, was also a predictor in a population of African-Americans.

Caucasians and African-Americans differ in how they keep their balance of parathyroid hormone and vitamin D, which is why it was not known if serum phosphorus levels would be a predictor in this specific patient population. Researchers conducted a retrospective analysis of 754 mainly African-American patients attending an urban clinic for CKD. All patients were assessed for their levels of blood phosphorus (normal values range from 2.4–4.1 milligrams per deciliter [mg/dL]), and were followed for a period of two to five years.

The results revealed that serum phosphorus was a statistically significant predictor of progression to the study end point of dialysis initiation. This result was observed even after researchers controlled for variables like race, sex, age, smoking status, BMI, diabetes, and other disease biomarkers. According to a news release, the authors concluded that, “The results suggest phosphorus may have independent negative consequences on CKD progression. Testing this would require trials that evaluate lowering serum phosphorus on progression to dialysis.”