estimated creatinine clearance for males =
= ((140 - (age in years)) * (body weight in kg) / (72 * (serum creatinine in mg/dL))) mL/min
estimated creatinine clearance for females =
= ((0.85) * (140 - (age in years)) * (body weight in kg) / (72 * (serum creatinine in mg/dL))) mL/min =
= (140 - (age in years)) * (body weight in kg) / (85 * (serum creatinine in mg/dL))) mL/min
Note: In the original reference, the formula is NOT per 1.73 meters-squared.
where:
• Body weight is the adjusted body mass (use ideal body weight if current body weight exceeds the ideal body weight, else use the current body weight)
• According to Robert et al (see below), a serum creatinine of 1 mg/dL should be used if the serum creatinine is under 1 mg/dL.
• According to Zawada, the calculated clearance should be reduced in patients with spinal cord injuries (20% if paraplegic; 40% if quadraplegic); source not given
|
GFR in mL/min
|
renal function
|
|
males 90-139;
females 80-125
|
normal
|
|
52 - 62.5
|
slight impairment
|
|
42 - 52
|
mild impairment
|
|
28 - 42
|
moderate impairment
|
|
< 28
|
severe impairment
|
Limitations:
• This applies for adults 20-100 years of age.
According to Robert et al (1993), using the lower value of actual vs ideal body weight and using a serum creatinine value of 1 mg/dL for actual serum creatinine values < 1 mg/dL, the GFR was more accurately predicted in critically ill patients using the Cockcraft-Gault equation rather than a 24 hour measured creatinine clearance; the latter tended to overestimate the actual clearance in many patients.
