Some of frequent questions are below, but if you have any other questions about the eGFR-C study please contact the study team .

If a potential participant has a history of alcohol or drug abuse but it has stopped, are they excluded from the study?

No, if the alcohol or drug abuse is not a current problem then the patient can be included in the study.

What should I do if our study blood pressure monitor has a problem?

The monitors are guaranteed until 17th February 2017. Before then it can be replaced – this should be arranged through Gillian Eaglestone, eGFR-C Lead Research Nurse ( geaglestone@nhs.net ).

Any operational queries can be individually telephoned or emailed to the dealer White Medical:
t: 01788 553904

What is the latest time the iohexol assessments can start?

As long as the participant adheres to the guidelines on permitted food, then the iohexol assessment can be started at any time before 12pm - as long as the participant is prepared to stay until as late as 4pm.

What time should be recorded as the start of the iohexol assessment?

The mid-point of the iohexol infusion will be used as the start of the assessment. The CRFs will ask you to record the start and finish times of the iohexol infusion and the database will calcuate the exact mid-point. When recording the subsequent blood sample times, please use the start time of the infusion to calculate the time (i.e. use 5 minutes from the start to work out the timing for the 5 minute sample).

The most important point is to accurately record the actual time, not to take the sample exactly 5 minutes later.

What should I do if a participant only has one arm available for sampling?

In some cases, such as if a female participant has severe lymphoedema after a mastectomy, a participant may only have one arm available for the iohexol administration and subsequent blood samples.

It is important not to sample from any high risk site. In this particular instance the approach is to use a single site for iohexol administration and blood sampling. The key is to ensure, as in the standard procedure, that that the iohexol is completely flushed in; nothing remaining in the line or any multi-way tap. Then as a second precaution, withdraw and discard the first 5ml of blood at the initial 5 minute sample.

Why are two needle sizes specified in the study guide?

The iohexol is quite thick and sticky and so it is better administered through the larger 21G needle. The finer, smaller 23G needles are kinder for repeated venepuncture in the event that you are unable to cannulate.

There is nothing in the in-pack safety leaflet about a recommended needle size. However, the 21G needle is what is generally easier for iohexol and has been specified in the study guide so that all sites follow the same procedure to limit possible variations.

Are meat and fish permitted before non-iohexol visits?

No; the permitted foods list should be followed from 10pm the night before in the same way as for iohexol assessments. Participants should be reminded of this if you speak to them before visits.

What ethnic groups can be included in the main study?

Any ethnic group can be included in the main study; participation is not restricted to the three ethnic groups targeted by the sub-study.

What ethnic groups can our site recruit into the sub-study?

If your site is taking part in the sub-study, you can recruit any of the ethnic groups targeted into the sub-study – stated targets for each site and group are intended as a guide to what the study team expects from your area to help the sub-study as a whole recruit the right number of participants in each group.

The groups eligible for the sub-study are: 31, 32, 33, 34 (Caucasian); 39, 40, 41 (South Asian); 44, 45, 46 (African Caribbean).

Are patients who have had a kidney removed eligible?

Yes, as confirmed in the study management group meeting on 10th September 2014, nephrectomy patients are eligible.

Are kidney transplant patients eligible?

No, patients who have received a kidney transplant are not eligible - the equations used have not been validated in this population.

The iohexol assessment CRF asks for recent Hb and HbA1c. What is recent?

A value from the last 12 months should be used, if available. They do not need to be taken specifically for the study.

A patient only had a partial iohexol injection. Can we use their samples?

No. If for any reason the full 5ml of iohexol is not injected, any subsequent blood samples cannot be used for the measured GFR test, so should not be taken. If the participant only had a partial iohexol injection due to a possible vasovagal reaction, you should probably not repeat the iohexol injection, and should therefore withdraw the participant. Discuss this with your Principal Investigator.

Do 6 monthly follow-up visits have to take place before midday?

No. It is preferable that follow up visits are held in the morning, but to be as pragmatic as possible for both sites and participants, it is acceptable to carry out these assessments after midday, as long as the permitted foods list has still been observed since 10pm the night before. If a follow up visit is going to be arranged for the afternoon, please remind your participants to stick to the permitted foods list.

No urine sample could be taken at baseline. Can it be taken later?

Yes. It is acceptable to take a urine sample at a later date – up to a month later if necessary.

No urine sample could be taken before the iohexol. Can it be taken after?

It is better to take the urine sample before the iohexol. However, it is a relatively small dose and we would prefer to get a post-iohexol urine sample than none at all.

Are patients with thyroid disease eligible for the study?

Yes – please note this condition on their baseline CRF.

A CKD3 patient has a GFR result outside the CKD3 range. Are they eligible?

A patient must have stage 3 CKD as defined by the protocol (GFR 30-59 mL/min/1.73 m2). There must be at least two consecutive tests within this range over 90 days – so there must be a clear 90 day period in the last year where the patient’s eGFR was within the acceptable limits.


  • If a patient’s only eGFR results are day 1 = 50, day 45 = 65, and day 91 = 50, they are NOT eligible. They do not have an eGFR of 30-59 for a period of 90 days.
  • If a patient’s only eGFR results are day 1 = 50, day 45 = 50, and day 91 = 50, they ARE eligible. They have an eGFR of 30-59 over a period of 90 days.
  • If a patient’s eGFR results at day 1 = 50, day 100 = 50, day 200 = 50 and day 210 = 65, they ARE eligible. They have an eGFR of 30-59 over a period of 90 days in the last year.
  • If a patient’s eGFR results at day 1 = 50, day 100 = 50, day 200 = 50, day 300 = 65, day 310 = 50, they ARE eligible. They have an eGFR of 30-59 over a period of 90 days in the last year.