endogenous creatinine clearance in mL/min =
= (((urinary creatinine in mg/kg/min) * (body weight in kg) * 100) / (serum creatinine in mg/dL))
The following equations were reported by Mawer et al based on linear regression equations based on the nomogram.
For men (page 15, Mawer et al, 1972):
daily creatinine output in males =
= ((body weight in kg) * (29.3 - (0.203 * (age in years)))) mg/day
For women (page 15, Mawer et al, 1972):
daily creatinine output in females =
= ((body weight in kg) * (25.3 - (0.175 * (age in years))))) mg/day
Alternatively, the female daily creatinine output can be estimated from the male output, as (page 76, Mawer et al, 1976):
daily creatinine output in females =
= 0.8 * (daily creatinine output for a male) =
= (0.8 * ((body weight in kg) * (29.3 - (0.203 * (age in years))))) mg/day
corrected daily creatinine output in mg/day =
= correction for inhibitory effect of a raised serum creatinine upon the 24-hour urinary output of creatinine =
= ((daily output for sex) * (1 - (0.03 * (serum creatinine in mg/dL))))
creatinine clearance in mL/min =
= (((corrected creatinine output) * 100 ) / ((serum creatinine in mg/dL) * 1440)) =
= ((corrected creatinine output) / ((serum creatinine in mg/dL) * 14.4))
where:
• The 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).
Limitations
• The estimate is too large if there is severe congestive heart failure (CHF) present.
