creatinine clearance - three methods reviewed

Creatinine Clearance Methods

Check out the creatinine clearance multi-calc

Option 1 uses the following equations::
Cockcroft and Gault equation utilizing the ibw (Ideal body weight) to calculate an estimated creatinine clearance.

Cockcroft and Gault equation:
CrCl = [(140 - age) x IBW] / (Scr x 72)       (x 0.85 for females)
Note: if the ABW (actual body weight) is less than the IBW use the actual body weight for calculating the CRCL. If the patient is >65yo and creatinine<1.0, use 1 to calculate the creatinine clearance.

(Note: Some clinician's feel that rounding the serum creatinine to 1.0 in the elderly will result in underestimation of clearance. Recommendation: Follow your local protocol.

Estimate Ideal body weight in (kg)
Males: IBW = 50 kg + 2.3 kg for each inch over 5 feet.
Females: IBW = 45.5 kg + 2.3 kg for each inch over 5 feet.

Option 2 (equations):
Cockcroft and Gault equation utilizing the adjusted body weight to calculate an estimated creatinine clearance.

CrCl =     [(140 - age) x AjBW]
                ---------------------------------
                         (Scr x 72)

Note: (Multiply result by 0.85 for females)
AjBW = adjusted body weight:
AjBW = IBW + 0.3( ABW - IBW)

Estimated IBW:
Males: IBW = 50 kg + 2.3 kg for each inch over 5 feet.
Females: IBW = 45.5 kg + 2.3 kg for each inch over 5 feet.

Key points: Note that the adjusted body weight equation uses 0.3 as a correction factor compared to the aminoglycoside's adjusted body weight equation which uses 0.4

Also, the adjusted body weight is not calculated unless the actual body weight is 25% greater than the ideal body weight. In all other cases, the ideal body weight is used.

Some studies have shown that utilizing the adjusted body weight improves accuracy compared to other commonly used equations in estimating the creatinine clearance in the elderly population.

Option 3 (equation):

Simplified 4-variable MDRD study formula¹¹

GFR = 186.3 x (SCR)^-1.154 x (age in years)^-0.203 x 1.212 (if patient is black) x 0.742 (if female)

Key point: Early statistical analysis shows very promising results. This may be especially true in chronic kidney disease.

Recommended review:
K/DOQI Clinical Practice Guidelines for Chronic Kidney Disease: Evaluation, Classification, and Stratification

References

1) Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16(1):31-41

2) Davis GA, Chandler MH. Comparison of creatinine clearance estimation methods in patients with trauma. Am J Health-Syst Pharm 1996;53:1028-32.

3) Dawson-Saunders B, Trapp RG. Basic and Clinical Biostatistics. 2nd ed. Norwalk, CT: Appleton & Lange; 1994.

4) Dettli LC. Drug dosage in patients with renal disease. Clin Pharmacol Ther 1974;16:274-80.

5) Drusano LG, Munice HL, Hoopes JM et al. Commonly used methods of estimating creatinine clearance are inadequate for elderly debilitated nursing home patients. J Am Geriatrics Soc 1998;36:437-41.

6) Hailemeskel B, Namanny M, Kurz A. Estimating aminoglycoside dosage requirements in patients with low serum creatinine concentrations. Am J Health-Syst Pharm 1997;54:986-7.

7) Jelliffe RW. Estimation of creatinine clearance when urine cannot be collected. Lancet 1971;1:975-6.

8) Levey AS, Greene T, Kusek JW, et al. A simplified equation to predict glomerular filtration rate from serum creatinine (Abstr) J Am Soc Nephrol 2000;(11):155A

9) Levey AS, Greene T, Schluchter MD, et al. Glomerular filtration rate measurements in clinical trials. Modification of Diet in Renal Disease Study Group and the Diabetes Control and Complications Trial Research Group. J Am Soc Nephrol 1993;4(5):1159-71

10) Levey AS. Assessing the effectiveness of therapy to prevent the progression of renal disease. Am J Kidney Dis 1993;22(1):207-14

11) Levey AS, Bosch JP, Lewis JB, et al. A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group. Ann Intern Med 1999;130(6):461-70

12) Rhodes RS, Sims PJ, Culbertson VL et al. Accuracy of creatinine clearance estimates in geriatric males with elevated serum creatinine clearance. J Geriatric Drug Ther 1991;5:31-45.

13) Smythe M, Hoffman J, Kizy K et al. Estimating creatinine clearance in elderly patients with low serum creatinine concentrations. Am J Hosp Pharm 1994;51:189-204.

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