Iohexol GFR

Description: 
This test is part of the transfer of services from the WellChild laboratory at the Evelina Children’s Hospital. Glomerular filtration rate (GFR) is determined by measurement of plasma clearance of iohexol. Iohexol, a contrast agent or dye, is injected into the bloodstream and blood samples are collected at specified time-points (5, 120, 180 and 240 min). Iohexol, creatinine, SDMA and ADMA are all measured by liquid chromatography mass spectrometry (LC-MS/MS) as part of this test. This test is performed using a defined protocol and dedicated request form. It requires accurately timed sample collection and patient information.

This test is not currently included in the laboratory's UKAS scope of accreditation to ISO15189:2022
Clinical details: 
Glomerular filtration rate (GFR) has been considered one of the best physiological measures of kidney function. Estimated glomerular filtration rate (eGFR) by equations based on creatinine and/or cystatin C are less accurate than measured GFR. In specific clinical situations the precision of the equations can be relatively poor and a measured GFR may be required.
Related condition or disease: 
Diabetes mellitus, chronic kidney disease (CKD), renal and non-renal transplantation, cirrhosis, heart failure
Synonyms or keywords: 
Iohexol GFR, mGFR, GFR, Iohexol,
Units: 
ml/min/1.73m2
Department: 
Biochemical Sciences Department
Location: 
St Thomas' Hospital
Sample type and Volume required: 
Lithium heparin plasma. Minimum sample volume 100 µL plasma, however smaller sample volumes can be accepted on occasion. If required, please contact the lab to discuss.
Patient instructions: 

Patients should have been sent information about the procedure beforehand. 

Special sample instructions: 

This test is performed using a defined protocol and dedicated request form. Accurately timed sample collection and patient information including height and weight are required. Samples that are received without a minimum of three forms of patient identifiable information will be rejected and will not be analysed. 

Criteria for acceptance / rejections of sample
Storage and transport: 
Samples should be sent immediately to central specimen reception (CSR) where they should be separated and the plasma immediately frozen ideally at or below -70 °C.
Contacts:
Inherited Metabolic Diseases Unit at St Thomas' Hospital
0207 188 9652
St Thomas' Hospital
North Wing - 4th Floor
London
SE1 7EH
For clinical advice or interpretation of results, please contact the laboratory in the first instance.
Laboratory: 
Inherited Metabolic Disease Laboratory at St Thomas'
Iohexol GFR request form
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Last updated: 30/07/2025