NONMEM Users Network Archive

Hosted by Cognigen

RE: Schwartz formulae

From: Mouksassi Mohamad-Samer <mohamad-samer.mouksassi>
Date: Tue, 31 Mar 2009 22:09:52 -0400

Dear Mahesh,

As any model the original equation of Schwartz is evolving over the =
years and as more data is gathered.

The original paper had only one k :

Schwartz GJ, Haycock GB, Edelmann CM Jr, Spitzer A. A simple estimate of =
glomerular filtration rate in children derived from body length and =
plasma creatinine. Pediatrics 1976; 58:259–263.

Then it was extended to other age groups to account for the maturational =
changes:

Schwartz GJ, Brion LP, Spitzer A. The use of plasma creatinine =
concentration for estimating glomerular filtration rate in infants, =
children, and adolescents. Pediatr Clin North Am 1987; 34:571–590.


Then other papers suggested different adjustment to the original =
formula... and to make it applicable for other age groups.


Please also note that the original k are applicable only for the =
old/standard Jaffe method to measure serum creatinine.
Newer methods require some adjustments.

Newer formulas are now published using cystatin and other markers.

Zappitelli M, Parvex P, Joseph L, et al. Derivation and validation of =
cystatin
C-based prediction equations for GFR in children. Am J Kidney Dis 2006;
48:221–230

(standard Schwartz formula may be misleading when we have renal =
impairment)
New equations to estimate GFR in children with CKD.
Schwartz GJ, Muņoz A, Schneider MF, Mak RH, Kaskel F, Warady BA, Furth =
SL.
J Am Soc Nephrol. 2009 Mar;20(3):629-37. Epub 2009 Jan 21.

Estimating and measuring glomerular filtration rate in children.
Work DF, Schwartz GJ.
Curr Opin Nephrol Hypertens. 2008 May;17(3):320-5. Review.


The right formula will depend on the nature of your pediatric population =
you want to calculate CRCL for , the method used for serum creatinine =
and whether you have some renally impaired children or not.

Hope this helps


Samer

-----Original Message-----
From: owner-nmusers
Sent: Tue 3/31/2009 16:09
To: nmusers
Subject: [NMusers] Schwartz formulae
 
Dear NMusers,
I am having difficulty with the Schwartz formulae for computing GFR in =
kids. Some references state that the formula gives GFR in mL/min while =
others say it is mL/min/1.73 mē. Also the value of k varies between =
references. This is what I plan on using. Are these formulas in the =
right units with the correct constants.

Please advise,
Mahesh

~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~=
*~*~*
Schwartz formula:
GFR (mL/min/1.73 mē) = k*Height(cm) / Serum Creatinine (mg/dL)
 
k = 0.33 in Preterm Infants
k = 0.45 in Term infants to 1 year old
k = 0.55 for children aged 2 to 12 years
k = 0.55 for girls 13 to 21 years, and
k = 0.70 for boys 13 to 21 years

GFR corrected for the child's actual BSA, which can be obtained using =
the DuBois and DuBois formula
GFR corrected = [GFR * 1.73] / BSA

The DuBois and DuBois formula:
BSA (mē) = (Weight^0.425 x Height^0.725) x 0.007184
where the weight is in kilograms and the height is in centimeters.

~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~=
*~*~*



Received on Tue Mar 31 2009 - 22:09:52 EDT

The NONMEM Users Network is maintained by ICON plc. Requests to subscribe to the network should be sent to: nmusers-request@iconplc.com.

Once subscribed, you may contribute to the discussion by emailing: nmusers@globomaxnm.com.