Date of publication: March 30, 2016

Expert Perspectives

Helping patients to achieve target phosphate levels – a question and answer session with Professor Fouque (Part 1)

In a new two-part video interview, Professor Denis Fouque from the Université de Lyon discusses how to help patients achieve target phosphate levels during a question and an answer session. In Part 1, Professor Fouque discusses:

  • The importance of phosphate binders for CKD patients
  • Why patients fail to reach recommended phosphate levels despite phosphate binder therapy
  • Reasons for poor adherence

Dialysis patients suffer from phosphate overload, which will lead to phosphate depositing into the tissues, and particularly vascular calcification. As a consequence,  because they have to eat protein, and proteins bring phosphate, they will have a phosphate overload.

– Professor Denis Fouque



In your expert opinion, why do dialysis patients need a phosphate binder?

Dialysis patients have to eat proteins every day to maintain their nutritional balance. Unfortunately, phosphate cannot be eliminated enough by the failing kidney. As a consequence, phosphate is increasing in the body and will lead to complications, particularly with calcium. The calcium phosphate products will induce tissue calcification, particularly vascular calcification.

In your expert opinion, what is the main reason for dialysis patients to take phosphate binders? What are the consequences if they do not take them?

Dialysis patients suffer from phosphate overload, which will lead to phosphate depositing into the tissues, and particularly vascular calcification. As a consequence, because they have to eat protein, and proteins bring phosphate, they will have a phosphate overload, which cannot be cleared by the kidney and will accumulate. When the dialysis patient eats protein, this leads to phosphate accumulation, and we need other ways to clear phosphate from the body.

Over the past ten years, you have been conducting a large observational study in France in dialysis patients. Could you outline the main results regarding hyperphosphatemia?

We conducted in France, a large observational study, called the Observatoire Phosphocalcique, for about 10 years [with] over more than 10,000 dialysis patients. What was very clear during this study, is that phosphate is still difficult to control. Hyperphosphatemia is present in more than 40% of patients who are taking [a] phosphate binder. So we clearly show, in this study, that approximately only 15% of patients were in the range of the KDIGO guidelines; and that 40% were still hyperphosphatemic and would need an increase in phosphate binders.

Why do you think so many patients fail to reach their recommended phosphate levels, despite being prescribed binders?

First of all, there is a paradigm in kidney disease in the sense that patients should eat proteins and they should limit their phosphate intake. [But] this is extremely difficult, because phosphate is linked strongly to proteins. One gram of protein brings 13 milligrams of phosphate. Then, if a patient is eating, for example, 100 grams of protein, he eats [1,300] milligrams of phosphate and then the phosphate accumulates into the body. Dialysis cannot take off all this phosphate from the body.

As a consequence, there is always a positive phosphate balance if the patient is eating sufficiently. So we cannot restrict protein from the patients, because this would induce malnutrition, which is extremely frequent during dialysis. Approximately, 30% to 40% of patients have malnutrition and protein-energy wasting; then the best way to control hyperphosphatemia would be to add phosphate binders.

Why is it difficult for patients to adhere to treatment?

The difficulty for the patient [in controlling] the increase in serum phosphate comes from the fact that they take a lot of pills every day. A dialysis patient routinely takes up to 20 pills per day. As a consequence, they may not be compliant enough, and they probably pick some of these drugs and they make a choice [on what to take]. The problem is to make [a] good choice. If they have too many pills, they will not take the right pills.

We know from experience that after one year, the compliance is about 50% to 60% only. This means that if you prescribe drugs, a patient may not take them. We have to find new ways to convince patients to be adherent to their medications, and particularly phosphate binders. Because patients do not see, urgently, the need to control phosphate as compared, for example, controlling blood glucose or blood pressure. So they may choose particularly to take these acute drugs, if I may say, and are not really convinced [on taking] medications that will protect them from five years [of] vascular calcifications, for example. We have addressed this point in a recent paper in [the] “American Journal of Kidney Disease,” showing how difficult it could be to balance nutrition and drugs in order to better control phosphate metabolism.

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