eGFR estimates how well the kidneys are filtering blood from a routine blood test, used to stage chronic kidney disease and assess overall health context in patients with respiratory or cardiopulmonary conditions.
κ = 0.7 (female) or 0.9 (male); α = −0.241 (female) or −0.302 (male).
G1 — normal filtration.
G2 — mildly decreased.
G3 — moderately decreased.
G4 — severely decreased.
G5 — kidney failure.
CURB-65 uses blood urea as one of its criteria, and kidney function directly affects urea levels, so understanding baseline kidney function helps interpret that value correctly.
≥90 normal (G1), 60–89 mildly decreased (G2), 30–59 moderately decreased (G3), 15–29 severely decreased (G4), and below 15 kidney failure (G5).
The 2021 CKD-EPI update removed the race coefficient used in older equations, part of an ongoing move toward race-neutral kidney-function estimation.
During rapidly changing acute kidney injury, because it assumes a stable, steady-state creatinine. It's a chronic-staging tool, not an acute one.