1. Infectious Diseases
Evaluation of the Chronic Kidney Disease Epidemiology
Collaboration Equation for Dosing Antimicrobials
Kurt A Wargo and Thomas M English
lomerular filtration rate (GFR) is
G the most accurate measure of one
of the major functions of the kidneys
BACKGROUND: Since the derivation of the Modification of Diet in Renal Disease
(MDRD) equation for estimating glomerular filtration rate (GFR), investigators
(clearance), though difficult and costly to determined that it cannot be used for drug dosing. In 2009, the Chronic Kidney
directly measure.1 Clinically, estimation of Disease Epidemiology Collaboration (CKD-EPI) derived an equation that was
more accurate than the MDRD estimation of GFR. Therefore, questions exist
GFR using the Modification of Diet in Re-
about which method should be preferred in making dosage adjustments for
nal Disease (MDRD) equation allows renally eliminated antimicrobials.
practitioners to stage chronic kidney dis- OBJECTIVE: To determine whether a difference exists when making antimicrobial
ease.2 When making estimations of kidney dosage adjustments in patients with CKD based on estimation of GFR using the
function at the bedside, for the purpose of CKD-EPI and Cockcroft-Gault equations.
drug dosing, practitioners utilize the Cock- METHODS: A database of 409 patients with CKD admitted to a tertiary care facility
croft-Gault equation.3 This equation esti- was used. GFR was calculated using both the CKD-EPI equation(s) and the
mates creatinine clearance (CrCl) and is Cockcroft-Gault equation and compared using correlation and Bland-Altman
recommended by the Food and Drug Ad- methodology. Dosage discordance rates of antimicrobials were determined.
ministration (FDA) for use by pharmaceu- RESULTS: Average GFRs for all patients using the Cockcroft-Gault and CKD-EPI
equations were 34.8 ± 12 mL/min and 39.9 ± 13 mL/min, respectively (5.09 [95% CI
tical companies when specific renal dos-
4.60 to 5.59]; p < 0.001). The correlation coefficient between the 2 estimations was
age adjustments are required.4 Since the high (r = 0.91). The Bland-Altman plot yielded limits of agreement of 15.3 and –5.1;
derivation of the MDRD equation and the thus, the CKD-EPI estimation may range from 5.1 mL/min below to 15.3 mL/min
finding that it was a more accurate predic- above the Cockcroft-Gault estimation for 95% of the cases. A discordance rate of
tor of renal function than the Cockcroft- 15–25% existed among the recommended dosing adjustments of the selected
Gault equation estimate, questions have antimicrobials when comparing the Cockcroft-Gault and CKD-EPI estimations.
existed with regard to its use for the pur- CONCLUSIONS: Though this study did not determine which equation should be
selected to dose adjust antimicrobials, it demonstrated statistically significant
pose of making drug dosage adjustments.2
differences between the Cockcroft-Gault and CKD-EPI equations. The clinical
To complicate matters, in 2009 a new set significance of these differences is uncertain in the absence of data assessing
of equations for the measurement of GFR, clinical outcomes that result from the use of the discordant doses. Clinical
derived from the Chronic Kidney Disease judgment should be employed when making renal dosage adjustments of
Epidemiology Collaboration (CKD -EPI) antimicrobials.
study, were found to provide a statistically KEY WORDS: antimicrobials, chronic kidney disease, CKD-EPI, Cockcroft-Gault,
more accurate estimation of GFR than the dosing, MDRD.
MDRD equation.5 Unfortunately, because Ann Pharmacother 2010;44:439-46.
Published Online, 17 Feb 2010, theannals.com, DOI 10.1345/aph.1M602
Author information provided at end of text.
theannals.com The Annals of Pharmacotherapy I 2010 March, Volume 44 I 439

2. KA Wargo and TM English
these equations estimate GFR and not CrCl, questions still proved observational analysis conducted at an 881-bed ter-
exist as to which method to use when estimating renal func- tiary care facility. A search engine was used to identify pa-
tion for the purposes of drug dosing in patients with CKD. tients admitted with a SCr of 1.3–3 mg/dL. Patients were in-
Differences exist between the CKD -EPI, MDRD, and cluded in the analysis if they were identified as having CKD
Cockcroft-Gault estimations of kidney function.2,3,5 One dif- by physician documentation and were classified as CKD
ference between the equations is that the 6-variable MDRD stages 3 (GFR 30–59 mL/min), 4 (15–29 mL/min), or 5
equation takes into account 3 biochemical markers, serum (<15 mL/min), using the MDRD equations. Excluded pa-
creatinine (SCr), serum albumin, and blood urea nitrogen tients were those with acute renal dysfunction, defined as an
(BUN), along with age, race, and sex. On the other hand, 8 elevation in SCr of 0.5 mg/dL from baseline, or from physi-
CKD -EPI equations exist, which take into account race, sex, cian documentation, end-stage renal disease on dialysis,
and SCr. The Cockcroft-Gault equation, on the other hand, is CKD stages 1 or 2, and those who were of a race other
dependent only on weight and SCr (Table 1). than white or African American.
One of the major responsibilities of pharmacists in- Estimation of GFR was performed using the CKD -EPI
volves making drug dosing adjustments based on estima- equations and MDRD equations normalized to body sur-
tions of renal clearance of medications. Therefore, it is in- face area (BSA) in order to determine the patient-specific
creasingly important that an equation that accurately esti- GFR in milliliters/minute.8 The Cockcroft-Gault estima-
mates this clearance is utilized when providing the most tion of renal function was used as the comparator equation,
optimal drug dosing recommendations. While both the in which the lower of actual or ideal body weight (IBW)
CKD -EPI and MDRD equations appear to more accurate- was used. For patients whose actual body weight exceeded
ly estimate GFR than does the Cockcroft-Gault equation, their IBW by greater than 30%, an adjusted weight was
they have not been validated for the purposes of making used in the calculation. Adjusted body weight was deter-
drug dosage adjustments. Numerous research studies have mined by the equation [(actual body weight – IBW) ≥ 0.4]
indicated that significant differences exist when comparing
+ IBW. Dosing discordance rates between the Cockcroft-
Cockcroft-Gault and MDRD equations for estimating re-
Gault and CKD -EPI equations were determined based on
nal function for the purposes of making dosage adjust-
the manufacturers’ renal dosing recommendations of 8
ments; however, this is the first study to compare the
common antimicrobials (Table 2).7,9 These antimicrobials
Cockcroft-Gault and CKD -EPI equations for this intent.6
were selected because the manufacturers’ recommenda-
tions for dosage adjustment in renal dysfunction were
Methods based on the Cockcroft-Gault equation.
The methods for this study have been previously de-
scribed.7 In short, this was an institutional review board–ap- STATISTICAL ANALYSIS
Data were compiled in Microsoft Access
(Microsoft Corp., Redmond, WA) and statisti-
cal testing was completed using SPSS soft-
Table 1. CKD-EPI Equations5
ware.10 Using the single proportion sample
Serum size measurement, a total of 247 patients were
Creatinine
Race and Sex (mg/dL) Equation needed to detect a 20% discordance rate with a
Black 95% confidence interval. Comparison of con-
female ≤0.7 GFR = 166 × (SCr/0.7)0.329 × (0.993)Age tinuous variables was performed by using
>0.7 GFR = 166 × (SCr/0.7)1.209 × (0.993)Age paired t-test and dichotomous variables were
male ≤0.9 GFR = 163 × (SCr/0.9)0.411 × (0.993)Age compared using the χ2 test, as appropriate.
>0.9 GFR = 163 × (SCr/0.9)1.209 × (0.993)Age Linear regression was incorporated to evaluate
White or other correlations between continuous variables, as
female ≤0.7 GFR = 144 × (SCr/0.7)0.329 × (0.993)Age appropriate. The Bland-Altman method was
>0.7 GFR = 144 × (SCr/0.7)1.209 × (0.993)Age used to assess agreement between the CKD -
male ≤0.9 GFR = 141 × (SCr/0.9)0.411 × (0.993)Age
EPI and Cockcroft-Gault estimations of renal
>0.9 GFR = 141 × (SCr/0.9)1.209 × (0.993)Age
function.11,12 χ2 Analysis was used to detect a
Single Equation GFR = 141 × min(SCr/k,1)α × max(SCr/k,1)–1.209 × 0.993Age
× [1.018 if female] × [1.159 if black], where α = –0.329 for difference in dosing discordance data. Level of
females and –0.411 for males; k = 0.7 for females and significance was set as p < 0.05. Data are pre-
0.9 for males; max = maximum of SCr/k or 1; and min =
minimum of SCr/k or 1.
sented as means (range) for continuous vari-
ables and as a number for dichotomous vari-
CKD-EPI = Chronic Kidney Disease Epidemiology Collaboration; GFR = ables, and 95% confidence intervals are report-
glomerular filtration rate; SCr = serum creatinine.
ed as appropriate.
440 I The Annals of Pharmacotherapy I 2010 March, Volume 44 theannals.com

3. Evaluation of Equation for Dosing Antimicrobials
Results equation was 39.9 ± 13 mL/min (Table 4). The absolute
mean difference between the 2 estimations was 5.10 ± 3.61
A total of 409 patients were eligible for evaluation in mL/min (95% CI 4.60 to 5.59; p < 0.001). Compared with
this analysis, as previously described.7 The mean ± SD age our previous data, the absolute mean difference in GFR,
of the cohort was 73.4 ± 12.5 years (Table 3). Patients using the MDRD and CKD -EPI equations, was 0.3 ± 0.22
were evenly distributed based on their sex, with the excep- mL/min (95% CI –0.14 to 0.76; p = 0.180).
tion of SCr, which was higher in males than in females (p A correlation coefficient was determined for the rela-
< 0.01). There was a preponderance of whites (81%) in the tionship of between calculated GFR using the CKD -EPI
cohort studied. Mean weight was 80 ± 23 kg, BSA was and Cockcroft-Gault equations among the patients evaluat-
1.90 ± 0.26 m2, BUN was 35 ± 16 mg/dL, SCr was 1.75 ± ed. Excellent correlation existed among all patients (r =
0.5 mg/dL. Among the cohort of patients sampled, 46% 0.91); however, the line of unity demonstrated that CKD -
weighed within 30% of their IBW, 36% exceeded their EPI estimations were consistently higher than Cockcroft-
IBW by greater than 30%, and another 18% weighed less Gault estimations of GFR (Figure 1). When comparing the
than their IBW. 2 estimates of GFR using the method described by Bland-
When estimating renal function, the average CrCl, using Altman, the difference in values was plotted against the
the Cockcroft-Gault equation, for all patients was 34.8 ± mean for the 2 methods in order to determine the variabili-
12 mL/min, whereas the average GFR using the CKD -EPI ty between them.10,11 The limits of agreement were 15.3
and –5.1; thus the CKD -EPI estimation may be 15.3
mL/min above or 5.1 mL/min below the Cockcroft-Gault
estimation for 95% of the cases (Figure 2). For the upper
Table 2. Manufacturer-Recommended Renal Dosing for limit of agreement, the confidence interval was 14.4 to
Selected Antimicrobials7,9 16.2 mL/min and for the lower limit, the confidence inter-
FDA-Recommended val was –6.0 to – 4.7 mL/min.
Antimicrobial CrCl (mL/min) to Adjust Dosage Antimicrobial dosage discordance rates were calculated
Cefazolin 10–30 to evaluate the difference between the estimations of renal
<10 function (Figure 3). It was determined that an overall dis-
Cefepime 30–60
11–29
cordant rate of 15–25% existed between the recommended
<11 dosing adjustments of the selected antimicrobials when
Daptomycin <30 comparing the Cockcroft-Gault and CKD -EPI estima-
Levofloxacin 20–49 tions. This discordant rate was lower than in our previous
10–19
study comparing the Cockcroft-Gault and MDRD estima-
Meropenem 26–50
10–25 tions, which found a difference of 20–36%.7 When com-
<10 paring the CKD -EPI and MDRD estimations, a 7–12%
Piperacillin/tazobactam 20–40 discordant rate was present. For the comparison of Cock-
<20
croft-Gault and CKD -EPI estimations, the majority
Trimethoprim/sulfamethoxazole 15–30
(88–96%) of discordance occurred when the manufacturer
CrCl = creatinine clearance; FDA = Food and Drug Administration. recommended a dosage adjustment; however, the dosage
adjustment was deemed unnecessary, accord-
ing to estimation by the CKD -EPI equation.
Table 3. Demographics7
Discussion
Female Male
Parameter (n = 208) (n = 201)
One well-recognized component of clinical
Age, y, mean (range) 75 (31–102) 72 (33–94) pharmacy involves renal dose adjustment of
African American, n 45 33 pharmacotherapy, when deemed appropriate.
SCr, mg/dL (mean ± SD) 1.66 ± 0.43 1.85 ± 0.55a The Pharmacy and Therapeutics committee at
BUN, mg/dL (mean ± SD) 34.6 ± 16.6 35.4 ± 15.2
our institution has approved the right of clini-
Actual weight, kg, mean (range) 77 (32–160) 83 (44–177)
cal pharmacists to dose-adjust medications
Ideal weight, kg, mean (range) 55 (43–84) 73 (55–94)
based on FDA-approved manufacturer recom-
Height, inches, mean (range) 64 (50–75) 70 (63–79)
Actual weight >130% of ideal weight, n 104 41a
mendations. This dosing modification may be
Actual weight <ideal weight, n 26 46a
done by pharmacists without prior approval
from the physician. Therefore, having an accu-
BUN = blood urea nitrogen; SCr = serum creatinine. rate estimation of renal function is of the ut-
a
p < 0.05.
most importance and has much clinical rele-
theannals.com The Annals of Pharmacotherapy I 2010 March, Volume 44 I 441

4. KA Wargo and TM English
vance. Ideally, clinical data such as urine output, nutrition- age adjustments to be statistically greater with the MDRD
al status, trends in SCr, and severity of illness would play a equation compared with the Cockcroft-Gault equation us-
more significant role in the decision by clinical pharma- ing actual body weight and the Cockcroft-Gault equation
cists to adjust doses as needed for renal function than the using IBW (88%, 85%, 82%; p < 0.001). The results of
estimates provided by equations. In reality, though, the use this large-scale study further validate the authors’ original
of equations to estimate renal function play a bigger role in 1999 findings that the MDRD equation is more accurate
this decision. Therefore, there is a strong need for estima- than Cockcroft-Gault estimations.2 Further, the authors
tions of renal function to be as accurate as possible and in suggest that, when the MDRD equation is normalized to
accordance with the method used by pharmaceutical com- BSA, it may be used for the purposes of drug dosing. Un-
panies in the development of renal dosing guidelines. fortunately, because of current FDA mandates, it is unrea-
In order to facilitate this process, and in accordance with sonable for the pharmaceutical industry to review all of
the Levey and colleagues2 data that demonstrated that their dosage recommendations based on the more accurate
MDRD estimations were more accurate than Cockcroft- MDRD, and now CKD -EPI equations. Further, with an
Gault estimations, our institution reports the 4-variable absolute difference in concordance of 3% between the
MDRD GFR in the routine chemistry panel of all patients. MDRD and Cockcroft-Gault estimation, it can be argued
However, there is a lack of literature to date that has evalu- that clinical significance does not differ between the 2.
ated the clinical utility of the MDRD or CKD -EPI equa- Therefore, continued use of the Cockcroft-Gault estima-
tions for making dosage adjustments of renally eliminated tion of renal function is rational.
medications. Further, considering that the FDA continues The findings of the present analysis demonstrate the ex-
to require that the pharmaceutical industry make dosage istence of a statistically significant difference when com-
adjustment recommendations based on the Cockcroft- paring the CKD -EPI and Cockcroft-Gault estimations of
Gault equation, it makes it difficult to advocate the use of renal function. Even though a strong correlation existed
MDRD or CKD -EPI. Finally, no equation gives an accu- when evaluating our entire cohort of patients, the Bland-
rate estimate of renal function in patients with fluctuating Altman method for assessing agreement demonstrated a
SCr concentrations; therefore, decisions to dose-adjust wide variation between the 2 estimations. Interestingly,
medications should not be made based on the results of a this variation was smaller than in our previous study com-
calculation of GFR at 1 moment in time. paring the Cockcroft-Gault and MDRD equations, 20.6
The existing literature comparing Cockcroft-Gault and and –9.8, though estimation of GFR was still higher with
MDRD estimations of kidney function demonstrates a sig- both of these equations compared with the Cockcroft-
nificant discordance between the 2 estimations.5 Since our Gault estimation.7 Additionally, based on the method cho-
original comparison, published in 2005, others have veri- sen to estimate GFR, antimicrobials in this analysis would
fied the discordance that exists between the 2 estima- still have been dosed differently 15–25% of the time, albeit
tions.5,13,14 In 2009, Levey and colleagues attempted to re- lower than our previous results comparing the MDRD and
solve the question of discordance between the MDRD and Cockcroft-Gault equations (20 –36%).7 These data imply
Cockcroft-Gault estimations by comparing their estima- that the CKD -EPI estimation is closer to the Cockcroft-
tions with a directly measured GFR (using iothalamate Gault estimation of renal function than is the MDRD.
clearance) in over 5500 patients.5 In their study, they found However, the possibility of clinically important differences
concordance rates with manufacturer-recommended dos- between the Cockcroft-Gault and CKD -EPI equations ex-
Table 4. Mean Difference in Cockcroft-Gault, CKD-EPI, and MDRD Equationsa,7
Cockcroft-Gault CKD-EPI GFR MDRD
GFR (mL/min), (mL/min), (mL/min),
Characteristic Mean ± SD Mean ± SD Mean ± SD p Valueb
Overall (n = 409) 34.8 ± 12.0 39.9 ± 12.5 40.2 ± 12.2 <0.001
Female (n = 208) 30.3 ± 10.9 34.5 ± 10.6 34.9 ± 10.3 <0.001
Male (n = 201) 39.5 ± 11.3 45.5 ± 11.9 45.7 ± 11.5 <0.001
White (n = 331) 35.4 ± 12.0 39.8 ± 12.4 40.0 ± 12.0 <0.001
African American (n = 78) 32.3 ± 11.7 40.2 ± 13.2 40.8 ± 13.1 <0.001
CKD-EPI = Chronic Kidney Disease Epidemiology Collaboration; GFR = glomerular filtration rate; MDRD = Modification of Diet in Renal Disease.
a
Based on demographics.
b
Statistical significance existed when comparing Cockcroft-Gault with both the CKD-EPI and the MDRD equations; no significant differences were
observed when comparing CKD-EPI and MDRD.
442 I The Annals of Pharmacotherapy I 2010 March, Volume 44 theannals.com

5. Evaluation of Equation for Dosing Antimicrobials
ist and merit further consideration, considering that 1 in 4 when the CKD -EPI estimation was used, leading to the
patients would have received a different dose of medica- potential for adverse reactions such as seizures, arrhyth-
tion based on equation selected. mias, renal failure, gastrointestinal symptoms, and neuro-
As stated previously, the majority of discordance existed muscular hypersensitivity. Although the potential for such
when the manufacturer recommended a dosage adjustment adverse reactions is quite low and may not bear clinical
according to the Cockcroft-Gault estimation, yet that par- significance, the variation between the 2 estimations was
ticular level of dosage adjustment was unnecessary accord- so great (15.3 to –5.1 mL/min), a clinically significant dif-
ing to GFR estimation by the CKD -EPI equation. Accord- ference may be implied. However, without actually admin-
ing to this rationale, in patients with discordant dosage rec- istering antimicrobials to the patients, directly measuring
ommendations, 88–96% would have been overdosed GFR, comparing that measurement to our estimations, and
Figure 1. Comparison of CKD-EPI and Cockcroft-Gault estimations of renal function for the study population using correlation (N = 409). The line of
unity demonstrates that CKD-EPI estimations of GFR are consistently higher than Cockcroft-Gault estimations in our population. CG = Cockcroft-Gault;
CKD-EPI = Chronic Kidney Disease Epidemiology Collaboration; GFR = glomerular filtration rate.
Figure 2. Comparison of CKD-EPI and Cockcroft-Gault estimations of renal function for the study population using Bland-Altman plot (N = 409). The
limits of agreement demonstrate that CKD-EPI estimations of GFR are 15.3 mL/min above to 5.1 mL/min below Cockcroft-Gault estimations in 95% of
cases. CG = Cockcroft-Gault; CKD-EPI = Chronic Kidney Disease Epidemiology Collaboration; GFR = glomerular filtration rate.
theannals.com The Annals of Pharmacotherapy I 2010 March, Volume 44 I 443

6. KA Wargo and TM English
assessing outcomes, clinical significance can only be im- analysis and the Levey and colleagues study.5 Of note, the
plied from this analysis. cohort of patients in the CKD -EPI study exhibited a mean
Interestingly, the discordance between MDRD and age of 47 ± 15 (internal validation set) and 50 ± 15 years
CKD -EPI dosing recommendations was quite small, rang- (external validation set), whereas our analysis consisted of
ing from 7% to 17%, indicating that little difference would a significantly older population, mean of 73.4 ± 12.5 years.
exist when making dosing recommendations based on ei- However, results from a study by Cirillo and colleagues
ther the CKD -EPI or MDRD equations. This, however, is suggests this difference may not be significant, as they
not entirely surprising given the data presented in the Lev- found the MDRD equation to be a more accurate predictor
ey and colleagues study,5 as well as the data from this of GFR than the Cockcroft-Gault equation in older pa-
study compared with our previous study.7 tients.16
This analysis contains various limitations, based on a A final limitation of this analysis lies within our method
series of assumptions. Measurement of actual GFR was of selecting patients. While we were able to recruit more than
not conducted on patients. Instead, we relied on the data a sufficient number of patients to power this analysis, we did
presented in the Levey and colleagues CKD -EPI study not include patients with SCr less than 1.3 mg/dL with sub-
to establish that GFR can be accurately estimated, using stantially decreased renal function or patients with SCr
their equation.5 Thus, the major limitation of this analy- greater than 3 mg/dL yet not on dialysis. Therefore, all of the
sis is associated with the comparison of 2 estimated val- possible patients with stages 3–5 CKD were not captured.
ues. Furthermore, drug concentration monitoring was Taking into consideration the data from the present
not performed during this analysis due to a lack of re- study, along with previously reported information, we
sources. agree with the comments by Stevens and colleagues when
Because the CKD -EPI equation was chosen as the com- they stated, “It is time to move beyond the focus on differ-
parator estimator of renal function, it becomes important to ences among equations and towards a focus on using the
control for patient demographic differences between this most accurate clinical data to improve the care of our pa-
Figure 3. Antimicrobial dosage discordance rate when comparing the MDRD and CKD-EPI estimations of GFR with the manufacturer-recommended
dosage adjustment using the Cockcroft-Gault estimation.7 CKD-EPI = Chronic Kidney Disease Epidemiology Collaboration; GFR = glomerular filtra-
tion rate; MDRD = Modification of Diet in Renal Disease; Pip/Tazo = piperacillin/tazobactam; Trim/Sulfa = trimethoprim/sulfamethoxazole.
Black bars = MDRD vs CKD-EPI.
White bars = Cockcroft-Gault vs CKD-EPI.
Dotted bars = Cockcroft-Gault vs MDRD.
444 I The Annals of Pharmacotherapy I 2010 March, Volume 44 theannals.com

7. Evaluation of Equation for Dosing Antimicrobials
tients.”17 The question should not be which equation we 13. Gill J, Malyuk R, Djurdjev O, Levin A. Use of GFR equations to adjust
drug doses in an elderly multi-ethnic group—a cautionary tale. Nephrol
use to dose-adjust antimicrobials but rather, “Is this the
Dial Transplant 2007;22:2894-9. DOI 10.1093/ndt/gfm289
only tool we need to use?”18 In our opinion, assessment of 14. Golik MV, Lawrence KR. Comparison of dosing recommendations for
clinical information of our patients should be the lone fac- antimicrobial drugs based on two methods for assessing kidney function:
tor when deciding to dose-adjust medications. Cockcroft-Gault and Modification of Diet in Renal Disease. Pharma-
cotherapy 2008;28:1125-32. DOI 10.1592/phco.28.9.1125
Results from previous studies have raised questions in 15. Stevens LA, Nolin TD, Richardson MM, et al. Comparison of drug dos-
the minds of clinicians as to whether the MDRD equation, ing recommendations based on measured GFR and kidney function esti-
and now the CKD -EPI equation, should be the preferred mating equations. Am J Kidney Dis 2009;54:33- 42.
DOI 10.1053/j.ajkd.2009.03.008
method to estimate renal function, in order to make critical
16. Cirillo M, Anastasio P, De Santo NG. Relationship of gender, age, and
decisions about medication dosing. Though the results of body mass index to errors in predicted kidney function. Nephrol Dial
this study show that the CKD -EPI equation is closer than Transplant 2005;20:1791-8. DOI 10.1093/ndt/gfh962
the MDRD equation to the Cockcroft-Gault estimations, 17. Stevens LA, Nolin T, Levey AS. In reply to ‘Estimated GFR for drug
dosing: a bedside formula,’ ‘Drug dose adjustments in patients with re-
statistically and potentially clinically significant differ- nal impairment,’ ‘Use of the MDRD study equation for drug dosing,’
ences still exist. It is our opinion that differences between and ‘Estimated GFR vs creatinine clearance for drug dosing.’ Am J Kid-
estimations of renal function will always exist and, ulti- ney Dis 2009;54:985-6. DOI 10.1053/j.ajkd.2009.08.017
mately, when faced with the decision to adjust dosages, 18. Wargo KA. Clinical judgment: to dose adjust antimicrobials or not. Phar-
macotherapy 2008;28:281e-3e.
clinical judgment should prevail.
Kurt A Wargo PharmD BCPS, Associate Clinical Professor, Harri-
son School of Pharmacy, Auburn University, Auburn, AL
Evaluación de la Ecuación del Chronic Kidney Disease
Thomas M English PhD, University of Alabama at Birmingham;
Huntsville Regional Medical Campus, Huntsville, AL Epidemiology Collaboration para Ajustes en Dosis de Agentes
Reprints: Dr. Wargo, 301 Governors Dr. SW, Suite 385C1, Antimicrobiales
Huntsville, AL, fax 256/551-4567, wargoka@auburn.edu. KA Wargo y TM English
Financial disclosure: None reported Ann Pharmacother 2010;44:439- 46.
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parison of the Modification of Diet in Renal Disease and Cockcroft- de correlación entre ambos estimados fue alto (r = 0.91). Los límites de
Gault equations for antimicrobial dosage adjustments. Ann Pharma- concordancia en la gráfica Bland-Altman fueron 15.3 y –5.1. El estimado
cother 2006;40:1248-53. DOI 10.1345/aph.1G635 de GFR calculado con la ecuación de CKD -EPI pudiera estar entre 5.1
8. DuBois D, DuBois E. A formula to estimate the approximate surface mL/min por debajo y 15.3 mL/min por encima del estimado con la
area if height and weight be known. Arch Intern Med 1916;17:863-71. ecuación CG en el 95% de los casos. Se observó una diferencia de 15 a
9. Lacy CF, Armstrong LL, Goldman MP, Lance LL. Drug information 25% en los ajustes de dosis recomendados de los agentes antimicrobiales.
handbook. 13th ed. Hudson, OH: Lexi-Comp, Inc., 2005. CONCLUSIONES: Este estudio demostró diferencias significativas en los
10. SPSS for Windows, Rel. 15.0.0., 2006. Chicago, IL: SPSS Inc. ajustes en dosis de agentes antimicrobiales al utilizar las ecuaciones
11. Bland JM, Altman DG. Statistical methods for assessing agreement be- CKD -EPI y CG. Se desconoce el significado clínico de estas diferencias
tween two methods of clinical measurement. Lancet 1986;1:307-10. ante la ausencia de datos que evalúen los resultados clínicos asociados
con la diferencia de las dosis calculadas. Se debe utilizar el juicio clínico
12. Bland JM, Altman DG. Applying the right statistics: analyses of mea-
al hacer ajustes en dosis de agentes antimicrobiales.
surement studies. Ultrasound Obstet Gynecol 2003;22:85-93.
DOI 10.1002/uog.122 Traducido por Astrid J García-Ortiz
theannals.com The Annals of Pharmacotherapy I 2010 March, Volume 44 I 445

8. KA Wargo and TM English
L’Evaluation d’Une Nouvelle Equation pour Estimer le Taux de hospitalier de soins tertiaires. Le TFG était calculé par les 2 équations à
Filtration Glomérulaire en Présence d’Insuffisance Rénale l’étude et les résultats évalués par des analyses de corrélation et une
analyse comparative de Bland-Altman. Le taux de discordance des
KA Wargo et TM English recommandations des ajustements posologiques dérivés de ces différents
Ann Pharmacother 2010;44:439- 46. estimés du TFG était finalement déterminé.
RÉSULTATS: Les valeurs moyennes de TFG étaient de 34.8 ± 12 mL/min
et de 39.9 ± 13 mL/min pour les formules CG et CKD -EPI, respective-
RÉSUMÉ ment (différence moyenne absolue 5.1; intervalle de confiance de 95%
INTRODUCTION: Plusieurs recherches démontrent que l’équation MDRD 4.6 – 5.59, p < 0.001). Une très bonne corrélation entre les 2 estimés a
(modification de la diète en présence de maladie rénale-Modification of été notée (r = 0.91). Selon les limites d’entente déterminées par l’analyse de
Diet in Renal Disease) pour évaluer le taux de filtration glomérulaire Bland-Altman, les estimés du TFG obtenus avec la formule CKD -EPI
(TFG) ne peut être utilisée pour guider les ajustements posologiques de pouvaient être, dans 95% des cas, inférieurs de 5.1 mL/min et supérieurs
différents médicaments. En 2009, le groupe d’épidémiologie sur de 15.3 mL/min par rapport aux valeurs obtenues par l’équation CG. Un
l’insuffisance rénale chronique (CKD -EPI) a proposé une méthode plus taux de discordance pouvait varier entre 15 et 25% au niveau des
précise que l’équation MDRD pour l’estimation du TFG. Ce nouvel différentes recommandations d’ajustements posologiques basées sur les
outil n’a toutefois pas été évalué dans un contexte d’estimation de la estimations de la fonction rénale à l’étude.
fonction rénale et de recommandation pharmacothérapeutique. CONCLUSIONS: Cette étude a démontré une différence statistiquement
OBJECTIF: L’objectif de cette étude est de déterminer s’il existe une significative entre les estimés du TFG obtenus par la formule CG et
différence entre les recommandations d’ajustements posologiques des l’équation CKD -EPI. La significative clinique d’une telle différence
antibiotiques en présence d’insuffisance rénale, lorsque ces demeure toutefois à être précisée. Un jugement clinique est donc nécessaire
recommandations sont basées sur l’estimation du TFG dérivé de la lors d’ajustements posologiques d’antimicrobiens pour un patient chez
formule Cockcroft-Gault (CG) et de l’équation CKD -EPI. qui l’estimation de la fonction rénale se fait par différentes méthodes.
MÉTHODOLOGIE: Il s’agit d’une étude rétrospective ayant évalué le Traduit par Sylvie Robert
dossier de 409 patients insuffisants rénaux admis dans un centre
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