Good day. I'm Dr. Glenn Chertow, Professor of Medicine and Chief of the Division of Nephrology at Stanford University School of Medicine. Today, I'm going to address the question, how are we doing managing phosphorus in our patients with CKD or chronic kidney disease on dialysis? The KDOQI and KDIGO Clinical Practice Guidelines provide recommendations for managing serum phosphate. How do these guidelines translate into clinical practice? In other words, how are we doing managing our patient's phosphorus? Data from several sources, including DOPPS, the dialysis outcomes practice pattern study suggests that we're not doing as well as we would like. A significant proportion of patients are not consistently achieving serum phosphate goals. Based on DOPPS data, 40% of patients had serum phosphate concentrations higher than 5.5 milligram per deciliter, and 69% had serum phosphate concentrations higher than 4.5 milligram per deciliter in the most recent month tested. When looking at serum phosphate concentrations from a sample of 1015 patient charts provided by 159 nephrologists across the United States, 42% of the phosphate binder treated patients had serum phosphate concentrations higher than 5.5 milligram per deciliter in the most recent month, consistent with findings from DOPPS.

However, a six-month analysis of the same chart audit data found that 77% of patients were unable to consistently maintain serum phosphate concentrations at or below 5.5 milligram per deciliter. This discrepancy in the one month versus six month chart audit data suggests that there is the potential to misclassify patients as having well controlled serum phosphate concentrations based on a single month evaluation when this may not be the case. Indeed, patients are often in and out of range from month to month, potentially due to variations in a number of factors, including dietary phosphorus consumption, phosphate binder intake, and parathyroid hormone concentrations. This chart audit data suggests that evaluating phosphate control based on a single month of data may underestimate the number of patients with uncontrolled or poorly controlled hyperphosphatemia. A recent study analyzed serial DOPPS data from over 17,000 individual patients to calculate the patient's phosphorus area under the curve referred to as the AUC. Using an AUC approach to monitoring hyperphosphatemia takes into account both the serum phosphate concentration and the amount of time a patient's serum phosphate concentration was above the target range.

An AUC of zero reflected patients whose serum phosphate concentrations were consistently controlled at or below 4.5 milligram per deciliter during the entire six-month period, whereas patients with higher AUC values had worse phosphate control. The AUC analysis demonstrated that in the United States, 93% of patients were unable to consistently maintain serum phosphate concentrations at, or below 4.5 milligram per deciliter during the six-month period with their current therapeutic regimen. This number is markedly higher than the 69% of patients in DOPPS whose serum phosphate concentrations were above 4.5 milligram per deciliter based on an assessment of a single monthly value. Taken together, the data suggests that poor phosphorus control is more prevalent than one month of data might suggest.

Perhaps, we have become accustomed to accepting that a significant proportion of our patients are not meeting serum phosphate targets because we understand that the medical arsenal currently available to us has limitations. We also recognize that we haven't fully understood how phosphorus absorption occurs. Our new mechanistic understanding that the paracellular pathway is the primary means by which dietary phosphorus absorption occurs has important implications. Targeting the paracellular pathway may improve our ability to achieve target serum phosphate concentrations. And thank you for your attention.