creatinineeGFR

Creatinine-based estimated glomerular filtration rate (creatinine-based eGFR) is an estimate of kidney function derived from serum creatinine measurements. It expresses how much blood plasma is filtered by the kidneys per minute, normalized to a standard body surface area of 1.73 m^2, and is reported as mL/min/1.73 m^2. eGFR is widely used in clinical practice to assess renal function and to screen for and stage chronic kidney disease (CKD).

Most eGFR calculations use either the MDRD Study equation or the CKD-EPI equation. These equations combine a person’s serum creatinine with demographic factors such as age, sex, and, in some versions, race to estimate GFR. Serum creatinine is measured using standardized laboratory assays and is ideally traceable to isotope dilution mass spectrometry (IDMS). The CKD-EPI equation generally provides more accurate estimates across a broad range of GFRs, particularly above 60 mL/min/1.73 m^2, though many laboratories still report both versions and may include or omit race coefficients depending on current guidelines.

Clinical use of creatinine-based eGFR includes screening for CKD, staging disease, guiding drug dosing, and monitoring changes in kidney function over time. It is an estimate rather than a direct measurement of GFR, so trends and context are important.

Limitations and caveats include sensitivity to muscle mass, diet, age, sex, and body size; results may be less accurate in elderly individuals, very muscular people, pregnant individuals, amputees, or those with unusual muscle mass. eGFR can be unreliable in acute kidney injury and in children. Additionally, some formulas incorporate race coefficients, a practice under review in many settings; cystatin C–based estimates can be used as an adjunct in selected cases.