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eGFR-C is a research study in seven NHS Trusts across England which has recruited 1249 patients to find out the best method of testing kidney function.

eGFR-C is no longer recruiting. Participants in eGFR-C are 18 or over and have been diagnosed with Stage 3 Chronic Kidney Disease (CKD). There are centres taking part in the study in Birmingham, Derby, Kent, Leicester, London and Salford - they are shown on the participating centres page here.

This research is designed to test different ways of estimating kidney function. The best way of measuring kidney function is time consuming and expensive, so estimates are normally used instead. eGFR-C will look at which method of estimating is most accurate for a UK population.

All participants in eGFR-C have consented to take part, and then they have a first assessment visit. At this, we take some blood samples (a total of 12 mL, about 3 teaspoons) and a urine sample for measurement of kidney function and store some blood and urine for measurement of other kidney markers in a central laboratory.

The research team then give a small injection of a substance called iohexol into a vein. Four further blood samples are  taken (4 mL, just under a teaspoon, each time) over a period of four hours to measure how efficiently the kidneys have cleared the iohexol injection from the participant's blood. In total the visit takes about five hours to complete.

Then there are follow-up visits in clinic at 6, 12, 18, 24 and 30 months to assess kidney function. These visits may be a part of routine hospital care and should be very short - around 10 minutes. At each of these visits we ask for a blood sample and a urine sample for tests of kidney function. The final visit will take place after 36 months. At this last visit all of the tests and measures from the first visit, including the iohexol injection, are repeated. This will be the end of the study and after this participants' care continues as normal.

Some participants are also taking part in a sub-study (an extra study within the main study) looking at what happens to chronic kidney disease with time. This involves having the iohexol injection at 12 months and 24 months as well as the initial and 36 months iohexol injection procedures.

After all 1249 participants have reached the three year test the results will be compared, analysed, and published.

Chronic Kidney Disease (CKD) affects more than 1 in 10 people in the UK, and over 50 million blood tests a year are used by the NHS to measure kidney function. Measuring kidney function is important as it helps to diagnose kidney disease and see if it is getting worse.

Usually, a substance in the blood called creatinine is measured to estimate kidney function. However, other substances can also be measured. One is cystatin C, and we want to find out if measuring this instead - or as well - gives a more accurate measurement of kidney function.

More accurate measurement of kidney function will allow doctors to diagnose and treat CKD better.

There are no risks other than a potential allergic reaction to the iohexol used in the gold standard test. The major disadvantage of participation in the study is that the iohexol test at the beginning and end of the study takes approximately five hours to complete.

Iohexol GFR measurement is a widely used procedure but very rarely people can have an allergic reaction to the iohexol. The dose of iohexol we are using is much lower than usually used in clinical practice. Sensitivity or allergy to iodine-based products means that you cannot be considered for participation in this research project. All participants have been asked by their research team about this.

The results from the blood and urine samples taken as part of the study will not be made available to participants or doctors until the participants complete the study so there is no immediate individual benefit from taking part in the study.

However, the information we get from the study should help us to improve the identification of kidney disease progression and the treatment of people with kidney disease in the future.

eGFR-C started recruiting in 2014, and the recruitment period lasted for 35 months, finishing in January 2017. 1229 patients were recruited into the main study. Another 20 joined a side-study based in Canterbury. Each patient is followed up every six months for three years. Once the last patient has had their three year follow up visit, there will be a 6 month period of data analysis and report writing before the study results are published.

The eGFR-C Chief Investigator is Dr Edmund Lamb, based at Kent and Canterbury Hospital.

The eGFR-C study is being co-ordinated by Birmingham Clinical Trials Unit, and is co-sponsored by the University Â鶹¾«Ñ¡ and East Kent Hospitals University NHS Foundation Trust.

The study has been funded by the National Institute for Health Research Health Technology Assessment programme (NIHR HTA Ref: 11/103/01).

All research in the NHS is looked at by an independent group of people called a Research Ethics Committee (REC) to protect your safety, rights, wellbeing and dignity. This study has been reviewed and approved on 9th October 2013 by South East Coast - Surrey REC (Reference No: 13/LO/1349). RECs include healthcare professionals as well as non-medical people, and are completely independent from anyone organising the study.

ISTRCTN42955626