About the PHOSPHATE trial

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A Pragmatic randomised trial of High or Standard Phosphate Targets in End-stage kidney disease - The PHOSPHATE trial

The kidneys maintain normal phosphate levels in the blood by excreting it into the urine. When kidneys fail, phosphate levels in the blood rise, and doctors believe this may be harmful to blood vessels and the heart. Consequently, most dialysis patients take medicines (up to 15 tablets per day) to lower phosphate. These are known as 'BINDERS' because they work by binding phosphate in the intestine before it is absorbed from the diet. Binders have many side effects, and patients struggle to take them. Binders are expensive, costing the NHS up to £5000 per patient per year. Despite this, there have never been any trials to test whether lowering blood phosphate with binders makes any difference in improving the health of dialysis patients by keeping the heart and blood vessels healthy, helping them feel better, or improving quality of life.

Does lowering blood phosphate with binders reduce angina, heart attack, stroke, circulation problems to the legs including amputation, or death from any of these causes?

Patients needing dialysis will be asked to participate in a randomised trial. Patients will be assigned to one of two groups: A) Intensive phosphate lowering (towards normal or a blood level less than 1.5 mol/L) or B) Liberal phosphate (blood level 2 to 2.5 mol/L). The intensive group will receive binders to reach a low phosphate; the liberal group will only receive binders if their blood phosphate goes very high (more than 2.5).

UK Patients taking part in the study will have only one study visit at the start of the trial. This is possible because information about the health of dialysis patients is routinely collected by the NHS. Dialysis patients can register on PatientView (https://patientview.org) or PatientKnowsBest (https://patientsknowbest.com/renal/) to allow them to view their own blood test results. PatientView or PatientKnowsBest is active in all kidney units in the United Kingdom. Hospital laboratories send blood test results on all registered patients to the UK Renal Registry (UKRR) or to PatientKnowsBest to provide patients with access to their own results via the PatientView or PatientKnowsBest website. We will use these datasets to monitor phosphate and will recommend changes to binder doses based on these results. The UKRR collects other information about dialysis patients which will also be sent to the trial team. The NHS collects information on anyone admitted to hospital (through NHS Digital or equivalent in Wales/Scotland). From this information we can establish whether patients have had serious illnesses. Using these existing data sources means that we do not need to call patients in for extra study visits. It also means the study will cost less than it might otherwise have done.

For this Study, 3,600 patients would need to participate. Since it may not be possible to enrol so many patients from the UK alone, we have joined forces with colleagues in Canada, Australia and New Zealand. Patients from all three countries may be enrolled in the study. We expect more than half to come from the UK.

The PHOSPHATE Trial is an investigator-initiated, international, multi-centre, prospective, randomised, open-label, parallel-group, superiority, and pragmatic large simple trial.

Recruitment for the PHOSPHATE trial began in April 2022 and will continue until April 2025.

The PHOSPHATE Trial protocol, UK appendix and Patient Information Sheet can be accessed here:

This study is funded by the National Institute for Health Research (NIHR) Health Technology Assessment Programme (NIHR127873). The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care.