Life is not always that simple.
Any additional cost is incurred for all tests. Benefits (if they exist at
all) are spread over only a few.
A single penny on a high volume test often leads to a very low benefit:cost
ratio.
This does not stand in isolation but has to be compared with the
benefit:cost ratio for any other procedure that competes for the same money.
If you are a patient that suffers because of an inferior method you will
naturally believe that the few additional pence on your particular test
would have been money well spent.
If, in contrast, you are the patient denied access to another medical
service because money has been spent on a more accurate method you might
challenge the need for that accuracy.
Yesterday John Duley posted his invitation together with his reflection on
the level of clinical scientist pay. It is no good having exceptionally
accurate methods unless we can pay enough to those who use them!
Trevor Tickner,
Norfolk and Norwich
-----Original Message-----
From: Jonathan Middle [mailto:[log in to unmask]]
Sent: 19 November 2002 13:43
To: [log in to unmask]
Subject: Re: "Compensated" creatinine
I would like to support and endorse David's comment. It is a
fundamental principle which we ignore at our peril.
The word 'traceability' is highly relevant here too!
Where a reference measurement system exists it must be used to
determine the trueness of field methods. The onus is on the
manufacturer to prove traceability of results back to a primary
standard. Have Roche done this and can they validate their
approach across a wide range of clinical samples??
Jonathan Middle
On 19 Nov 2002, at 9:44, David Cook wrote:
> Oren Zinder wrote:-
>
> "The enzymatic creatinine determination seems not to suffer from this
> problem, yet it is much more expensive".
>
>
> It seems to me the important thing is to be using methods that are
> accurate, given that we have a choice. If that is the cost of getting
> an accurate result, then that is the cost of getting an accurate
> result. What is the cost of getting the answer wrong, for this or any
> other analyte? Do anyone's accountants factor that one in?
>
> Surely the better method is that which is more accurate, not that
> where the results require to be derived by what appears to be no more
> than an arithmetical fiddle for a systematic method error which may
> not be constant from patient to patient.
>
> Best wishes
>
>
> David Cook
>
>
>
> Dear all,
>
> We use the rate-blanked Jaffe method for creatinine on our automated
> (Roche 747) analyzers.
>
> Recently we have been informed by Roche that in order to correct for
> the serum matrix error they are altering their calibrator (Cfas) and
> subtracting 26.5 umol/L (0.3 mg/dl) from the result of the
> determination. They require us to do the same with our patient
> samples.
>
> Although this correction is certainly valid in its reasoning, this
> mathematical subtraction (no change in reagent or protocol) results in
> a substantial change in the creatinine results which we will be
> reporting, especially in children where we often have
> "non-compensated" levels of creatinine around 35 - 62 umol/L (0.4-0.7
> mg/dl).
>
> In addition, since urine does not have the same matrix problem,
> calculation
> of the CCT using the "compensated" serum creatinine levels results in
> a much higher clearance value (dividing by the lower serum values -
> sometimes half of what they used to be).
>
> The enzymatic creatinine determination seems not to suffer from this
> problem, yet it is much more expensive.
>
> I would greatly appreciate comments on this problem,
>
> Thanking you all in advance,
>
> Oren Zinder
>
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============================================
Jonathan Middle, UK NEQAS Birmingham
tel 0121 414 7300 fax 0121 414 1179
This message is intended only for the above
recipient(s). The opinions expressed are
mine alone and do not necessarily represent
those of UK NEQAS Birmingham, the University
Hospital Birmingham NHS Trust or the UK NEQAS
Organisation.
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