Table 3.

Illustrative estimates of glomerular filtration rate (eGFR) in the US. Measurement of glomerular filtration rate (GFR) represents the blood filtered by the kidney, often measured by fructose-based polysaccharide (i.e., inulin) that is neither secreted nor reabsorbed across tubules. Most clinical measures use estimates of GFR via assessment of creatinine, which is a breakdown product from muscle, and thus correlates with muscle mass. Some estimates of GFR are not validated for obesity. Salazar-Corcoran includes body weight as a variable, but not commonly used in clinical practice [80]. CKD-EPI and MDRD may be indexed (adjusted) for body surface area. However, it is unclear that indexing or deindexing improves accuracy among patients with obesity [80,84,85].

Measure of estimated glomerular filtration rate (eGFR)	Formula variables	References
Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is frequently used by US commercial labs. In patients with obesity, the CKD-EPI may overestimate chronic kidney disease and underestimate glomerular hyperfiltration in patients with obesity.	Equation includes serum creatinine adjusted for age, gender, and race (Black or not Black), and not adjusted for weight. Data from non-US countries suggest the CKD-EPI equations without race-ethnicity adjustment are more appropriate.	[78,79]
Abbreviated Modification of Diet in Renal Disease (MDRD) equation is sometimes used in US clinical trials. CKD-EPI may be more accurate than MDRD for patients with BMI ≥30 kg/m2 and with higher eGFR (>60 ml/min/1.73 m2)	Equation includes serum creatinine, adjusted for age, gender, and race (Black or not Black) and not adjusted for weight. It is estimated that that without the MDRD eGFR race adjustment, 3.3 million (10.4%) more Black Americans would reach a diagnostic threshold for Stage 3 chronic kidney disease, 300,000 (0.7%) more would qualify for beneficial nephrologist referral, and 31,000 (0.1%) more would become eligible for transplant evaluation and waitlist inclusion.	[[80], [81], [82]]
Cockcroft-Gault equation is rarely used in clinical practice, but is the historic standard used in for renally-adjusted drug dosing studies	Serum creatinine, age, and gender adjusted for body weight. Cockcroft-Gault may be inaccurate in patients with obesity and underweight.	[83]