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)
• 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
• 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).
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Purpose: To use the method of Jelliffe for estimating the creatinine clearance when the serum creatinine is unstable.
Specialty: Nephrology, Clinical Laboratory
Objective: laboratory tests