Multiple Creatinine Clearance Methods and CKD Staging

Patient Name:
Location:

Age:
Scr:
Gender:

Select serum creatinine reference standard: [more info]

Height:
Weight:

For MDRD and CKDEPI equation. specify race:

Is the serum creatinine (Scr) currently stable:

Staging: Has the patient had kidney damage or
GFR <60 ml/min/1.73m^{2 }for
3 months
Chronic kidney disease: "defined as kidney damage or GFR < 60 ml/min/1.73m^{2 }for
3 months.
Kidney damage is defined as pathologic abnormalities or markers of damage,
including abnormalities in blood or urine tests or imaging studies." ^{9}

Restrict the maximum calculated clearance to this value:

Select option for calculating the IBW for patients under 60 inches
(default option  BMI method):
[See reference section] 

Creatinine Clearance methods

Cockcroft and Gault equation utilizing the tbw (Total body
weight) to calculate an estimated creatinine clearance

Cockcroft and Gault equation:
CrCl = [(140  age) x TBW] / (Scr x 72) (x 0.85 for females) 
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.
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. 
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 + 0.4( 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.
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. 
Simplified 4variable MDRD study formula

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. May
represent the most accurate choice of this group. This may be especially
true in chronic kidney disease. 
CKDEPI equation

GFR = 141 x min(Scr/κ,1)^{α} x max(Scr/κ,1)^{1.209}
x 0.993^{Age} x 1.018 [if
female]
x 1.159 [if black]
κ = 0.7 if female.
κ = 0.9 if male.
α = 0.329 if female
α = 0.411 if male
min = the minimum of Scr/κ or 1
max = the maximum of Scr/κ or 1
"BACKGROUND: Equations to estimate glomerular filtration
rate (GFR) are routinely used to assess kidney function. Current
equations have limited precision and systematically underestimate
measured GFR at higher values."^{ 1}
"CONCLUSION: The CKDEPI creatinine equation is more accurate than
the Modification of Diet in Renal Disease Study equation and could
replace it for routine clinical use."^{ 13}

References

 Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum
creatinine. Nephron 1976;16(1):3141
 Davis GA, Chandler MH. Comparison of creatinine clearance estimation
methods in patients with trauma. Am J HealthSyst Pharm 1996;53:102832.
 DawsonSaunders B, Trapp RG. Basic and Clinical Biostatistics. 2nd ed.
Norwalk, CT: Appleton & Lange; 1994.
 Demirovic JA, Pai AB, Pai MP. Estimation of
creatinine clearance in morbidly obese patients. Am J Health Syst Pharm.
2009 Apr 1;66(7):6428.
"An LBW estimate, based on TBW and BMI,
incorporated into the CockcroftGault equation provided an unbiased,
relatively precise, accurate, and clinically practical estimate of
24hour 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 CockcroftGault_{TBW}
grossly overestimated measured CL_{cr}. The CockcroftGaultABW_{0.3},
CockcroftGaultABW_{0.4}, and SalazarCorcoran
equations all overestimated measured CL_{cr} values in the study patients. In
contrast, the CockcroftGault_{IBW} and the MDRD4 equations
underestimated measured CL_{cr} values. The CockcroftGault_{LBW}
equation was the most precise, and the MDRD4 equation was the least. The
CockcroftGault_{FFW} and Cockcroft Gault_{LBW}
equations yielded the highest accuracy (5561%), in yielding values that
were within 30% of the measured CL_{cr}. 
 Dettli LC. Drug dosage in patients with renal disease. Clin Pharmacol
Ther 1974;16:27480.
 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;36:43741.
 Hailemeskel B, Namanny M, Kurz A. Estimating aminoglycoside dosage
requirements in patients with low serum creatinine concentrations. Am J
HealthSyst Pharm 1997;54:9867.
 Jelliffe RW. Estimation of creatinine clearance when urine cannot be
collected. Lancet 1971;1:9756.
 KDOQI Clinical Practice Guidelines for Chronic Kidney Disease:
Evaluation, Classification, and Stratification. © 2002 National Kidney
Foundation. (link)
 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
 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):115971
 Levey AS. Assessing the effectiveness of therapy to prevent the
progression of renal disease. Am J Kidney Dis 1993;22(1):20714
 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):46170
 Levey AS, Stevens LA, Schmid CH, Zhang YL, Castro AF 3rd, Feldman HI,
Kusek JW, Eggers P, Van Lente F, Greene T, Coresh J. A New
Equation to Estimate Glomerular Filtration Rate.
Ann Intern Med. 2009; 150:604612.
 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;5:3145.
 Salazar DE, Corcoran GB: Predicting creatinine clearance and renal
drug clearance in obese patients from estimated fatfree body mass. Am J
Med 84: 10531060, 1988.
 Smythe M, Hoffman J, Kizy K et al. Estimating creatinine clearance in
elderly patients with low serum creatinine concentrations. Am J Hosp Pharm
1994;51:189204.
 Wilhelm SM, Pramodini KP. Estimating
Creatinine Clearance: A Metaanalysis. Pharmacotherapy 2011 31:7 ,
658664.
"Conclusion. Using the CockcroftGault 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
CockcroftGault equation. Based on this analysis, the use of total body
weight, ideal body weight, and a rounded Scr value cannot be
recommended." 

Winter MA, Guhr KN, Berg GM. Impact of various body weights and
serum creatinine concentrations on the bias and accuracy of the
CockcroftGault equation. Pharmacotherapy 2012; 32: 604612 [PMID:
22576791 DOI: 10.1002/j.18759114.2012.01098.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 SalazarCorcoran
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 patient’s weight to a fatfree weight
or lean body weight predicted a Clcr calculated with the CG
equation without bias. Notably,
our study included 2065 obese or morbidly obese patients, far
more than other published studies.
Conclusions: An unbiased CG 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 CG Clcr. Rounding Scr in patients with low
Scr did not improve accuracy or bias of the Clcr calculations.


Background info for height less than 60 inches

If the actual body
weight is less than any of the calculation methods, the actual body
weight will be used. Discussion of the various methods: The
output of this section is based on research I had completed ~20 years
ago on this subject. A quick review of the recent literature has
not changed or added any new methods for estimating an ideal body weight
for patients less than 60 inches tall. Note: naming convention is
based on my earlier work...
1] Intuitive Method: Reference: Murdaugh LB. Competence Assessment Tools for
HealthSystem 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. This provides support for the
next method below.
2] Baseline Method:
The baseline method starts with the initial ideal body weight baseline
values e.g. 60 inch male patient  50kg and 60 inch female patient 
45.5kg. Male patient: 50kg /60 inches = 0.833 kg/inch.
Female patient = 45.5kg/60 inches = 0.758 kg/inch. Therefore
a male patient  55 inches: IBW = 50kg  (0.833 x 5) = 45.8kg versus the
first method = 50kg  (2.3 x 5) = 38.5 kg.
[Reference: reasonable assumption based on the standard ideal body weight
equations and the baseline weights established for a height of 60 inches. Also review: Murphy JE. Introduction. In: Murphy JE, ed. Clinical Pharmacokinetics, 5th ed. Bethesda, MD: American Society of HealthSystem Pharmacists, 2011:xxxiv.
 Note: for patients who are less than 60 inches tall, the weight should be decreased more conservatively than 2.3kg/inch.]
3] BMI method:
References:
Wiggins, K. L. (2004). Renal care: Resources and practical applications.
Chicago: American Dietetic Association. pg 12.
Barash, P. G., Cullen, B. F., & Stoelting, R. K. (1989). Clinical anesthesia.
Philadelphia: Lippincott. chap:47:1231
Remember that BMI = weight(kg)/height^{2} (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/m^{2}). Example: the following
patients all have a BMI ~ 21: 130 lbs  5'6", 163 lbs  6'2",
107 lbs  5'.
BMI

19

20

21

Height
(inches)

Body
Weight (pounds)

58 
91 
96 
100 
59 
94 
99 
104 
60 
97 
102 
107 
61 
100 
106 
111 
62 
104 
109 
115 
63 
107 
113 
118 
64 
110 
116 
122 
65 
114 
120 
126 
66 
118 
124 
130 
67 
121 
127 
134 
68 
125 
131 
138 
69 
128 
135 
142 
70 
132 
139 
146 
71 
136 
143 
150 
72 
140 
147 
154 
73 
144 
151 
159 
74 
148 
155 
163 
4] Hume method:
LBW (Males) = (0.3281 x Weight in kg) + (0.33939 x Height in cm) 
29.5336
LBW (Females) = (0.29569 x Weight in kg) + (0.41813 x Height in cm) 
43.2933
Using the example above: (55 inch male patient): IBW=
36.9 kg
Reference: Hume R. Prediction of lean body mass from height and
weight. J Clin Path(1966), 19, 389.
