Serum Phosphorus Levels Not Affected by Race, Income
African-American patients, however, had significantly higher intact parathyroid hormone levels, possibly due to lower 25-hydroxyvitamin D levels.
Victoria A. Kumar, MD, and her colleagues at Kaiser Permanente in Los Angeles, examined phosphorus levels from 4,862 end-stage renal disease patients who initiated HD at their institution. All patients had their serum phosphorus measured a median 7 times and had other tests of mineral metabolism. Using more than 68,000 phosphorus calculations, the investigators performed various analyses including by patients' estimated income and racial group, defined as Asian, White, Hispanic, African American, or “other.”
Race and income did not affect phosphorus levels, despite marked differences in socioeconomic status, according to results published in the Journal of Renal Nutrition. Roughly 2 in 3 African-American and Hispanic patients had an annual family income below $40,000 annually compared with more than 2 in 5 Asian and White patients. More White than minority patients were highly educated.
Only small differences in phosphorus control emerged. Asian patients experienced a significant 0.11 mg/dL per year increase in serum phosphorus levels. Time-average phosphorus levels were lower among Hispanic (4.33 mg/dL) and African American patients (4.4 mg/dL) than Asian (4.54 mg/dl) and White patients (4.48 mg/dl). White patients were older and had the lowest prevalence of diabetic kidney disease.
Racial differences in other markers of mineral metabolism did appear, however. African-American patients had significantly higher intact parathyroid hormone levels, possibly due to lower 25-hydroxyvitamin D levels. Serum calcium and albumin levels also differed, but were probably not clinically significant.
Good management of patients, such as early referral to nephrology and use of dietitians and renal pharmacists, may have compensated for disparities. “Aggressive and repeated education by staff regarding the importance of a low phosphorus diet and proper use of phosphate binders may play a role in maintaining phosphorus levels in target range…,” the investigators wrote. Educational material was easy to understand and available in Spanish. An integrated healthcare team stepped in with a plan of care whenever patients failed to meet target phosphorus levels.
Limitations of the study include incomplete lab reports for some patients and use of geocoding to estimate income and education.