De-indexed estimated glomerular filtration rates: A simple step towards improving accuracy of drug dosing of renally excreted medications in moderate to severe obesity.

ABSTRACT

Kidney function is underestimated in obese individuals when standard equations are applied. Laboratory-reported estimated glomerular filtration rates (eGFR) report glomerular filtration rates corrected for body surface area in mL/min per 1.73 m2 using modification of diet in renal disease or the chronic kidney disease-Epidemiology Collaboration equations. This may result in premature discontinuation or reduction in dosage of renally excreted medications. Currently, there are no clinical guidelines defining thresholds beyond which physicians should consider de-indexing patient eGFR values. We compared standard and de-indexed eGFR values for 281 consecutive patients seen in our chronic kidney disease clinic. In our study, half of the patients with a body mass index above 35 had clinically significant changes in their eGFR, with an improvement in chronic kidney disease stage, when eGFR was de-indexed. We propose that eGFR de-indexing should be considered in patients with moderate to severe obesity when calculating the dose, especially for medications that are excreted by the kidneys.