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Creatinine Clearance Methods

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Inputs

Patient Name:    Location:
Age (years):     Height: 10.0 inches    Weight: 10.0 kg
Gender: Male        SCR (mg/dl): 0.6

Analysis

BSA: M2        BMI kg/M2
Ideal body weight: kg
Adjusted body weight (AjBW) = IBW + 0.4( ABW - IBW): kg
Lean Body Weight (LBW):  kg
Percent over/under IBW: %
Warnings:   

* Patients with relatively low serum creatinine values e.g. <0.6 mg/dl may be inappropriate with some estimated clearance methods. Specialized references should be consulted. In the meantime, the serum creatinine will be adjusted upward to 0.6 mg/dl.

* Patients at extremes of weight require a modified approach and some of the listed clearance methods may be inappropriate. Specialized references should be consulted to determine appropriate actions.

*Note: height is less than 60 inches. Out of ~4 possible options, the BMI method was chosen to estimate the IBW. Subtracting 2.3 kg for each inch below 60 inches is extreme. See reference section.

Clearance Method / Calculated Value

Note: Program will provide guidance as to the most appropriate value based on available evidence and current inputs.  A flashing LED will appear near this value.   CommentsBased on a calculated BMI greater than 40 (155.00 kg/m2) - Morbidly Obese, the latest evidence (least bias) recommends the use of the CG equation using the adjusted body weight. There is also some support (fewer patients studied) for the use of the CG-LBW equation - see references.
Jelliffe: (ml/min)
Jelliffe (adjusted for BSA) (ml/min)
   Cockcroft & Gault (Ideal Body Weight): (ml/min)
   Cockcroft & Gault (Actual body weight): (ml/min)
Cockcroft & Gault (No body weight)17: (ml/min)

Consider These Results For Obese Patients

(Usually >30% over IBW) - Currently 614.29 percent over IBW. Note program also analyzes other factors such as BMI and decides which equation is preferred - look for a flashing LED.
led   Cockcroft & Gault using Adjusted BW: (ml/min)
led    Cockcroft & Gault utilizing LBW:4    ml/min

Reporting section

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Inputs:
===================
Patient Name:    Location:

Age (years):     Height: 10.0 inches    Weight: 10.0 kg
Gender: Male        SCR (mg/dl): 0.6




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Analysis:
===================
BSA: 0.20 M2        BMI155.00 kg/M2
Ideal body weight: 1.40 kg
Adjusted body weight: 4.8 kg
Lean Body Weight (LBW):  2.3 kg
Percent over/under IBW: 614.29 %



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Review any warnings or comments:
===================
Warnings:   

* Patients with relatively low serum creatinine values e.g. <0.6 mg/dl may be inappropriate with some estimated clearance methods. Specialized references should be consulted. In the meantime, the serum creatinine will be adjusted upward to 0.6 mg/dl.

* Patients at extremes of weight require a modified approach and some of the listed clearance methods may be inappropriate. Specialized references should be consulted to determine appropriate actions.

*Note: height is less than 60 inches. Out of ~4 possible options, the BMI method was chosen to estimate the IBW. Subtracting 2.3 kg for each inch below 60 inches is extreme. See reference section.


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Clearance Method / Calculated Value
===================
Note: Program will provide guidance as to the most appropriate value based on available data and current inputs.  A flashing LED will appear near this value. Based on a calculated BMI greater than 40 (155.00 kg/m2) - Morbidly Obese, the latest evidence (least bias) recommends the use of the CG equation using the adjusted body weight. There is also some support (fewer patients studied) for the use of the CG-LBW equation - see references.
Jelliffe: 190.0 (mL/min)
Jelliffe (adjusted for BSA)22.0 (mL/min)

Cockcroft & Gault (Ideal Body Weight): 4.5 (mL/min)
Cockcroft & Gault (Actual body weight): 32.4 (mL/min)




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Consider These Results For Obese Patients
===================
(Usually >30% over IBW) - Currently 614.29 percent over IBW. Note program also analyzes other factors such as BMI and decides which equation is preferred - look for a flashing LED.

Cockcroft & Gault  (Adjusted BW): 15.6 (mL/min) led
Cockcroft & Gault utilizing LBW:4  7.5  ml/min led


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. Demirovic JA, Pai AB, Pai MP. Estimation of creatinine clearance in morbidly obese patients. Am J Health Syst Pharm 2009; 66: 642-648 [PMID: 19299371 DOI: 10.2146/ajhp080200]

    "An LBW estimate, based on TBW and BMI, incorporated into the Cockcroft-Gault equation provided an unbiased, relatively precise, accurate, and clinically practical estimate of 24-hour measured CLcr in morbidly obese patients."

    Lean body weight - male:   9270 x tbw/6680 + 216 x BMI
    Lean body weight - female:  9270 x tbw/8780 + 244 x BMI

    Obese study population: As expected, use of Cockcroft-GaultTBW grossly overestimated measured CLcr. The Cockcroft-GaultABW0.3, Cockcroft-GaultABW0.4, and Salazar-Corcoran equations all overestimated measured CLcr values in the study patients. In contrast, the Cockcroft-GaultIBW and the MDRD4 equations underestimated measured CLcr values. The Cockcroft-GaultLBW equation was the most precise, and the MDRD4 equation was the least. The Cockcroft-GaultFFW and Cockcroft- GaultLBW equations yielded the highest accuracy (55-61%), in yielding values that were within 30% of the measured CLcr.
  5. Dettli LC. Drug dosage in patients with renal disease. Clin Pharmacol Ther 1974;16:274-80.
  6. Dooley MJ, Singh S, Rischin D. Rounding of low serum creatinine levels and consequent impact on accuracy of bedside estimates of renal function in cancer patients. Br J Cancer 2004; 90: 991-995 [PMID: 14997195 DOI: 10.1038/sj.bjc.6601641]
  7. 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.
  8. 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.
  9. Jelliffe RW. Estimation of creatinine clearance when urine cannot be collected. Lancet 1971;1:975-6.
  10. 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
  11. 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
  12. Levey AS. Assessing the effectiveness of therapy to prevent the progression of renal disease. Am J Kidney Dis 1993;22(1):207-14
  13. 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
  14. 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.
  15. Salazar DE, Corcoran GB: Predicting creatinine clearance and renal drug clearance in obese patients from estimated fat-free body mass. Am J Med 84: 1053-1060, 1988.
  16. 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.
  17. Wilhelm SM, Kale-Pradhan PB. Estimating creatinine clearance: a meta-analysis. Pharmacotherapy 2011; 31: 658-664 [PMID: 21923452 DOI: 10.1592/phco.31.7.658]
    "Conclusion. Using the Cockcroft-Gault equation with no body weight (NBW) and actual Scr value most closely estimated measured Clcr. In obese patients, it may be reasonable to use actual body weight with a correction factor of 0.3 or 0.4 and actual Scr value in the Cockcroft-Gault equation. Based on this analysis, the use of total body weight, ideal body weight, and a rounded Scr value cannot be recommended."
  18. Winter MA, Guhr KN, Berg GM. Impact of various body weights and serum creatinine concentrations on the bias and accuracy of the Cockcroft-Gault equation. Pharmacotherapy 2012; 32: 604-612 [PMID: 22576791 DOI: 10.1002/j.1875-9114.2012.01098.x]

    Quotes: [Largest study so far....total of 3678 patients]
    Regarding Salazar equation: This equation, however, was not consistently shown in studies to be a superior predictor of renal function. It is not widely used in clinical practice and has not been validated in pharmacokinetic studies. In addition, the Salazar-Corcoran equation is not recognized by the National Kidney Foundation.

    Regarding CG -LBW equation: Our findings do not support those conclusions and are different from a recent investigation of Clcr in 54 morbidly obese patients that found that adjusting an obese patientís weight to a fat-free weight or lean body weight predicted a Clcr calculated with the C-G equation without bias. Notably, our study included 2065 obese or morbidly obese patients, far more than other published studies. 

    Conclusions: An unbiased C-G Clcr can be calculated using actual body weight in underweight patients and ideal body weight in patients of normal weight. Using ABW0.4 for overweight, obese, and morbidly obese patients appears to be the least biased and most accurate method for calculating their C-G Clcr. Rounding Scr in patients with low Scr did not improve accuracy or bias of the Clcr calculations.  top of page

Other:  Estimating IBW in patients under 60 inches

BMI method
Remember that BMI = weight(kg)/height2 (meters squared).   Next, we will establish an 'ideal' BMI based on values in the standard IBW equations: Male: 60 inches - 50kg - BMI= 21.53.   Female: 60 inches - 45.5kg - BMI= 19.59.  We can then use this association to generate an equivalent ideal weight based on this standardized BMI and the height of the patient.  Using the example above (55 inch male patient):
IBW = 21.53 (BMI value above)  x (55 x 0.0254)2  = 42 kg.
Background info: the body mass index quantifies the amount of tissue mass at a particular height (units: kg/m2).  Example: the following patients all have a BMI ~ 21:  130 lbs - 5'6",  163 lbs 6'2",  107 lbs 5'

References:
Wiggins, K. L. (2004). Renal care: Resources and practical applications. Chicago: American Dietetic Association. p12.

Barash, P. G., Cullen, B. F., & Stoelting, R. K. (1989). Clinical anesthesia. Philadelphia: Lippincott. chap:47:1231


Intuitive Method:
Reference: Murdaugh LB. Competence Assessment Tools for Health-System Pharmacies. 5th ed. Bethesda, MD: ASHP; 2015. [Chap:29 Medication dosing in Patients with Renal Dysfunction]
IBW (Male) = 50kg - 2.3kg for each inch below 60 inches
IBW (Female) = 45.5kg - 2.3kg for each inch below 60 inches
Comments:  For patients just a few inches below 60 inches, the result is reasonable, however, 2.3 kg/inch is excessive when used for shorter heights.  At 38 inches for a male, and 40 inches for a female, the IBW is ZERO.  
Murphy JE. Introduction. In: Murphy JE, ed. Clinical Pharmacokinetics, 5th ed. Bethesda, MD: American Society of Health-System Pharmacists, 2011:xxxiv.  Note: for patients who are less than 60 inches tall, the weight should be decreased more conservatively than 2.3kg/inch.

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All calculations must be confirmed before use. The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgement. Neither GlobalRPh Inc. nor any other party involved in the preparation of this program shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.   Read the disclaimer
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