Martin
Given that the enzymatic creatinine is about eight times the cost, now would not be a good time to change. We only use it for paediatrics, jaundiced patients and where interference is suspected. If the core regional lab takes over your cold work, I suspect that they will only use Jaffe.
Roy
>>> "Myers Martin (LTHTR)" <[log in to unmask]> 04/08/2010 15:46 >>>
The Jaffe reaction is a non-specific colorimetric assay published in
1886 to give a rough estimation of creatinine (Jaffe, M Z. Physiol Chem,
10, 391 (1886). Whilst this was a significant advance in the 19th
Century, I think that as 21st Century Clinical Biochemists we should
perhaps move our subject on a bit use the enzymatic method for all
patients. I have been using it for some time and would recommend it to
my learned colleagues!
Martin
________________________________
From: Clinical biochemistry discussion list
[mailto:[log in to unmask]] On Behalf Of COLLINS MICHAEL
(RM1) Norfolk and Norwich University Hospital
Sent: 03 August 2010 18:20
To: [log in to unmask]
Subject: Re: Calculate GFR
My comparisons of enzymatic creatinine, compensated Jaffe and
uncompensated Jaffe found that compensated Jaffe was worse than
uncompensated Jaffe at low levels. We only run enzymatic creatinine on
young children.
Mike Collins
BMS3
Biochemistry Automation
Norfolk & Norwich University Hospital
England
[log in to unmask]
http://www.nnuh.nhs.uk/
________________________________
From: Clinical biochemistry discussion list
[mailto:[log in to unmask]] On Behalf Of McKillop, Derek
Sent: 03 August 2010 17:01
To: [log in to unmask]
Subject: Re: Calculate GFR
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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