DeltaDOT GFR test – Should this be the standard kidney function test in paediatric and advanced staged cancer patients?
15 min read.
Chemotherapeutic agents used to treat cancer require accurate dosing to prevent serious adverse toxicities. For those drugs excreted through the kidney, a precise understanding of kidney function (as measured by glomerular filtration rate, GFR) is needed to ensure drug toxicity is avoided. Carboplatin is unique among chemotherapeutic agents in that its dosing is largely based on the estimated GFR (eGFR) (McMahon and Rosner, 2020).
The standard way to assess the GFR, in humans, is to measure the creatinine levels, then estimate the GFR by using the CDK-EPI Creatinine Equation (2021) recommend by the National Kidney Foundation (Delgado et al., 2022). However, eGFR as a diagnostic test is unreliable to detect early stages of kidney dysfunction and has been shown to vary within individuals over time (Rahn et al., 1999). Additionally, commonly used GFR estimation equations were validated in cohorts with minimal representation of patients with cancer, therefore, further reducing its accuracy (Kitchlu et al., 2018).
DeltaDOT offers a diagnostic test that directly measures kidney function by using iohexol (an X-ray contrast medium) as a filtration marker. Both high performance liquid chromatography (HPLC) and DeltaDOT’s high performance capillary electrophoresis (HPCE) can be used to measure iohexol concentration, however, DeltaDOT’s HPCE is quicker and more cost-effective than HPLC (Devanur et al., 2014). Although, eGFR methods are cheaper than measured GFR (mGFR) methods, mGFR methods are far more accurate (as shown below).
The range which estimated vs measured GFR tests detect kidney dysfunction – Estimated GFR tests, which use creatinine or Symmetric Dimethylarginine (SDMA), detects renal dysfunction when GFR is reduced by 75% to 40%. Measured GFR test, which uses iohexol (as DeltaDOT uses), detects all stages of renal dysfunction. (Image provided by the DeltaDOT team)
As DeltaDOT offers a cost effective mGFR test, should this be the standard kidney function test in paediatric and advanced stage cancer patients?
This problem of the inaccuracies of standard GFR tests used in cancer patients have also been highlighted by these reviews: (McMahon and Rosner, 2020, Claudel et al., 2023). For more information on the DeltaDOT GFR test, pleases visit: http://www.deltadot.com/application-notes-downloads/ .
CLAUDEL, S. E., GANDHI, M., PATEL, A. B. & VERMA, A. 2023. Estimating kidney function in patients with cancer: A narrative review. Acta Physiol (Oxf), 238, e13977.
DELGADO, C., BAWEJA, M., CREWS, D. C., ENEANYA, N. D., GADEGBEKU, C. A., INKER, L. A., MENDU, M. L., MILLER, W. G., MOXEY-MIMS, M. M., ROBERTS, G. V., ST PETER, W. L., WARFIELD, C. & POWE, N. R. 2022. A Unifying Approach for GFR Estimation: Recommendations of the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease. Am J Kidney Dis, 79, 268-288 e1.
DEVANUR, L., PELLIGAND, L., HASSARD, S. & ELLIOTT, J. 2014. GFR measurements in feline subjects using high performance capillary electrophoresis. Journal of Veterinary Pharmacology and Therapeutics, 35, 174-174.
KITCHLU, A., SHAPIRO, J., AMIR, E., GARG, A. X., KIM, S. J., WALD, R. & HAREL, Z. 2018. Representation of Patients With Chronic Kidney Disease in Trials of Cancer Therapy. JAMA, 319, 2437-2439.
MCMAHON, B. A. & ROSNER, M. H. 2020. GFR Measurement and Chemotherapy Dosing in Patients with Kidney Disease and Cancer. Kidney360, 1, 141-150.
RAHN, K. H., HEIDENREICH, S. & BRÜCKNER, D. 1999. How to assess glomerular function and damage in humans. Journal of Hypertension, 17, 309-317.