 ### Description

Jelliffe proposed an equation to estimate the creatinine clearance when the serum creatinine is unstable.

creatinine clearance in mL/min =

= ((V * ((creatinine yesterday) - (creatinine today))) + P) * (100/1440) / (average creatinine)

where:

• Since creatinine is given in mg/dL, the volume of distribution for creatinine is given in dL.

• V = volume of distribution for creatinine in dL (dL used since serum creatinine in mg/dL) = 0.4 * (body weight in hundreds of grams)

• P is estimated creatinine production (see below)

• average creatinine = ((today's creatinine) + (yesterday's creatinine)) / 2

• If the serum creatinine is rising, (today's creatinine) is substituted for (average creatinine) in the equation.

• 1440 is the number of minutes in 24 hours

estimated creatinine production in mg/day =

= A * B * C

where:

• A = (29.305 - (0.203 * (age in years))) * (body weight in kilograms)

• (29.305 - (0.203 * age)) = (140 - (age) / 5), as used in the equation in section 12.01.05.09

• B = (1344.3 - (43.76 * (average creatinine))) / (1344.3 - (43.76 * 1.1)) = (1.037 - (0.0338 * (average creatinine)))

• C = 0.85 for males; for women it is 0.9 * (male value), or approximately (0.85 * 0.85), which works out to about 0.765 ; Jelliffe added the factor since the original equation without it gave too high an estimate (page 21).