Craig

 

 We are also wrestling with the issue of which formula we should be recommending. If we follow the recommendation “not to estimate GFR for children when using an alkaline picrate (“Jaffe”) method that has calibration traceable to IDMS ”  (see link below) we should therefore only be analysing creatinine in children using the enzymatic assays and calculating eGFR by the new Schwartz formula.

http://nkdep.nih.gov/labprofessionals/labgfr_children.htm

http://nkdep.nih.gov/professionals/gfr_calculators/idms_schwartz.htm

 

 

The problem is that our paediatricians currently use the old formula which has different k values for different developmental stages.  The new formula has only one k value and in his paper (   http://jasn.asnjournals.org/cgi/rapidpdf/ASN.2008030287v1.pdf

) Schwartz cautions that the formula may not be valid in children with normal body habitus.

 

The risk therefore is that by introducing a single k formula we inadvertently increase the inaccuracy in specific developmental stages than would be the case if we were to use the old formula but with the new ID-MS values.

 

 

Prof Schwartz has indicated to me that studies are ongoing to address this matter and should be published soon.

 

Sorry to have generated more questions than answers.

 

 

 

Derek McKillop PhD FRCPath

Principal Clinical Scientist 

Dept Clinical Biochemistry

Craigavon Area Hospital

Southern Health and Social Care Trust

Internal Extension: 3709

Direct Line: 028 38613709

 

-----Original Message-----
From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of Webster Craig
Sent: 03 August 2010 15:42
To: [log in to unmask]
Subject: Calculate GFR

 

Hi,

 

Our users would like to start calculating GFR based on creatinine results for children based on the Counahan-Barrett equation, basically the idea is we use a lookup table giving the median height for a child of the patient's age, and use that to calculate GFR. We would use a modified Counahan-Barrett equation, which in SI units is GFR=(40*HT)/Cr. We have relied on the literature overview and guidelines from the US Renal organisation KDOQI.

 

From what I can see this equation is based on a study done by Morris et al,  Arch Dis Child which was done in 1982 using a Jaffe / Alkaline picrate reaction with LKB autoanalyser.  We currently use a Roche Modular creatinine method calibrated using an ID-MS traceable calibrator.

 

Does anyone know of or implemented a similar system but have related the calculation to more recent methods?

 

Cheers

Craig

 

 

Craig Webster

Consultant Clinical Scientist

Birmingham Heartlands Hospital

Birmingham

B95SS

 

 

 

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