Below you will find an abstract which makes you reconsider the use of the
cockcroft formula for GFR determination. This was published in the journal
of the Dutch Society for Clinical Chemistry 2 years ago. I have no data on
the MDRD calculation.
Bart Ballieux
Can the Cockcroft formula be used as method to estimate the creatinine
clearance? The measurement of the creatinine clearance in a large group of
students. Comparison of the formula of Cockcroft and Gault and the classical
method
J.H.M.SOUVERIJN1, M.FRÖLICH2 , P.H.E.M.de MEIJER3 and A.E.MEINDERS3
Central Laboratory for General Physicians Leiden 1; Clinical Chemistry
Laboratory 2 and Department Internal Medicine 3, Leiden University Medical
Center, Leiden, The Netherlands
Introduction: First year medical students have been asked to
take part in an experiment to compare the results of the measurement
of the clearance of creatinine in the classical manner
using creatinine measurements in bloodsamples and in 24 hrscollections
of urine to those using the formula of Cockcroft
and Gault (CG). A total of 126 students (39 male, 87 female)
took part (89 % of the whole group). No criteria for in- or exclusion
have been used.
Methods: The clearance was measured and calculated as
"Clearance of creatinine (ml/min)= (number of mmol creat
excreted per 24 hours in urine)*1.000.000/ (concentration of
creat in serum(micromol/l )*1440)". The Cockcroft and Gault
formula consists of: "Clearance (ml/min)= (140-age(yrs))
*weight(kg)*1.26/serumcreat(micromol/l ). For females 1.26
is replaced by 0.99."
Results and discussion: The CG-clearances correlate weakly
with the measured clearance (R= 0.6). The best correlation of
the CG-clearances was a weak correlation (R=0,7) with the
weights, while the measured clearances correlate strongest
with the amounts of creatinine excreted in 24 hrs (R=0,9).
These results explain the poor correlation between the CGresults
and the measured creatinine clearances. The levels of
serum creatinine only correlate weakly with the creatinine
clearance. Analyzing the results according to Bland-Altman a
mean difference +/- SD was found between CG-results and the
measured clearance of 0 +/- 40. The differences show a negative
correlation with the mean values.
Conclusion: 1. the Cockcroft formula is not valid for estimation
of the creatinine clearance within this group of students of
approximately the same age; 2. the measured creatinine clearance
correlates strongly with the excretion of creatinine in
urine; 3. the use of the Cockcroft formula to illustrate the effect
of age on the clearance will be influenced by the weight
of the patient.
Dr. B.E.P.B. Ballieux
Clinical Biochemist
Leiden University Medical Centre
P.O.box 9600
2300 RC Leiden
The Netherlands
Tel:+3171-5262165/2278
Fax: +3171-5266753
email: [log in to unmask]
-----Original Message-----
From: McNeely, Michael [mailto:[log in to unmask]]
Sent: donderdag 13 februari 2003 16:43
To: [log in to unmask]
Subject:
The emerging trend in North America follows the guidelines recently
published by the National Kidney Foundation of the USA.
The NKF K/DOQI Guidelines can be located at
http://www.kidney.org/professionals/doqi/kdoqi/toc.htm and have been
described (Eknoyan G, Levey AS, Levin NW, Keane WF. The national epidemic of
chronic kidney disease. What we know and what we can do.
Postgrad Med. 2001 Sep;110(3):23-9.)
Essentially, what is recommended is that the GFR is calculated using the
MDRD calculation (see guidelines). This requires the s-creatinine
concentration and the age and gender of the patient. The reported GFR is
then linked to a classification table and the classification, in turn, to
Clinical Practice Guidelines.
Thus, the s-creatinine (and what reference range to express) becomes
secondary.
Michael McNeely MD FRCPC
[log in to unmask]
Vancouver BC Canada
-----Original Message-----
From: Paul Masters [mailto:[log in to unmask]]
Sent: February 12, 2003 3:24 AM
To: [log in to unmask]
Subject: Creatinine reference ranges
I am interested in whether, and how, colleagues report age and sex related
adult creatinine ranges. Serum creatinine is higher in men at all ages,
no doubt due to muscle mass. But male creatinine ranges are much more skewed
at older ages. My view is to report a different ULN for women
and men, but to use the young adult values for all ages and not to age
correct. (ULNs 100 umol/l for women, 120 umol/l for men.) Although it
may be common for the elderly to have higher creatinines ( Whitehead's BUPA
tables suggest 183 umol/l as the 97.5%ile for men >72, for
example) it is not desirable as it reflects decreased GFR. My concern is
that clinicians would be falsely reassured that renal function was normal
and not modify their prescribing of renally-excreted drugs appropriately.
What do other people do: single adult range, sex-related only, or age and
sex-related?
Paul Masters
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical
community working in clinical biochemistry.
Please note, archived messages are public and can be viewed
via the internet. Views expressed are those of the individual and
they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical
community working in clinical biochemistry.
Please note, archived messages are public and can be viewed
via the internet. Views expressed are those of the individual and
they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical
community working in clinical biochemistry.
Please note, archived messages are public and can be viewed
via the internet. Views expressed are those of the individual and
they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
|