Assessment of kidney function: clinical indications for measured GFR

Abstract

In the vast majority of cases, glomerular filtration rate (GFR) is estimated using serum creatinine, which is highly influenced by age, sex, muscle mass, body composition, severe chronic illness and many other factors. This often leads to misclassification of patients or potentially puts patients at risk for inappropriate clinical decisions. Possible solutions are the use of cystatin C as an alternative endogenous marker or performing direct measurement of GFR using an exogenous marker such as iohexol. The purpose of this review is to highlight clinical scenarios and conditions such as extreme body composition, black race, disagreement between creatinine- and cystatin C-based estimated GFR (eGFR), drug dosing, liver cirrhosis, advanced chronic kidney disease and the transition to kidney replacement therapy, non-kidney solid organ transplant recipients, and living kidney donors where creatinine-based GFR estimation may be invalid. In contrast to the majority of literature on measured GFR (mGFR), this review does not include aspects of mGFR for research or public health settings but aims to reach practicing clinicians and raise their understanding of the substantial limitations of creatinine. While including cystatin C as a renal biomarker in GFR estimating equations has been shown to increase the accuracy of the GFR estimate, there are also limitations to eGFR based on cystatin C alone or the combination of creatinine and cystatin C in the clinical scenarios described above that can be overcome by measuring GFR with an exogenous marker. We acknowledge that mGFR is not readily available in many centres but hope that this review will highlight and promote the expansion of kidney function diagnostics using standardized mGFR procedures as an important milestone towards more accurate and personalized medicine.

The ideal drug dosage adaptation through estimated glomerular filtration rate in obese patients? Measuring GFR is the key

“…“Measuring GFR is costly and cumbersome” is the sentence frequently used to justify estimating GFR. We could also add “GFR measurement is not standardized.” However, once again, measuring GFR is not required in every patient and in every clinical context, but in specific situations where a high precision is needed for GFR measurement and/or in patients with specific characteristics (such as obesity and hyperfiltration) which make the usual biomarkers inadequate 2,10 . The extra‐cost of the procedure must also be balanced with the potential benefits of measuring GFR.…”

The Glomerular Filtration Rate: From the Diagnosis of Kidney Function to a Public Health Tool

“…In some clinical situations, such as patients with anorexia nervosa, cirrhosis, obesity, evaluation of living kidney donors, prescribing nephrotoxic drugs with a narrow therapeutic window, pharmacokinetic studies of drugs excreted by the kidney, or any situation in which eGFR is unreliable, it is reasonable to measure GFR (mGFR), despite the added cost and time and resources consuming (7,(50)(51)(52). At present, iothalamate or 51Cr-EDTA or 99Tcm-DTPA urinary clearance or 99Tcm-DTPA or iohexol plasma clearance are the accurate methods for determining mGFR (52)(53)(54)(55).…”

Creatinine-based GFR-estimating equations in children with overweight and obesity

“…GFR is indexed with BSA, allowing comparison among children and adults [1,[8][9][10][11]. Although indexation of GFR for BSA for individuals with altered body proportions is a controversial topic [2,12,13], almost all current creatinine-based GFR-estimating equations have been designed for GFR indexed with BSA [1,4].…”