Iohexol plasma clearance measurement protocol standardization for adults: a consensus paper of the European Kidney Function Consortium

International consensus supports the development of standardized mGFR protocols to facilitate the implementation of more widespread and routine mGFR testing in clinical care and research protocols. With support from the EKFC, an international group of experts performed an extensive literature search to develop recommendations for a standardized approach to determine mGFR. This consensus paper evaluated the evidence and formulated recommendations that include all aspects of iohexol plasma clearance measurement in adults not on dialysis. These recommendations include practical advice for patient preparation, preparation and administration of iohexol, blood sample collection and sampling times, laboratory analysis, mathematical calculation of mGFR, as well as aspects concerning the safety of the procedure and implementation strategies. Iohexol plasma clearance can be measured following a multisample or single-sample protocol. Iohexol plasma clearance testing is contraindicated in patients with significant edema or ascites, or with a documented severe allergy to an iodinated contrast agent. Supplementary materials are provided to assist with the mGFR calculation using either MSP or SSP. Once the infrastructure for iohexol plasma clearance measurement is established, an mGFR implementation program will facilitate the incorporation of the mGFR into both clinical practice and research protocols, including importantly future efforts to develop and validate more accurate GFR estimation equations.