Brian
I posted a similar question a few months ago because we had traditionally
stated 36U/L as the upper limit for ALT, but when an academic colleague gave
us 'normal' data from patients randomly selected from GP lists the 97.5th
centile was 53 (Beckman LX20). Because of the skewed (long tail) data it
meant that the 95th centile was considerably lower at 43.
So where to set it? Our gastroenterologists were divided, but all agreed 36
was too low. However some felt 53 would miss many patients with pathology,
especially NASH. We therefore settled on 45, not as the upper limit of the
reference range, but as an 'action limit' for clinicians.
Which raises the point of whether we should quote reference ranges or action
limits. It seems obvious that some of the rise in ALT is due to the fact
that we are heavier and drink more than our ancestors. But we still define
obesity as >30kg/m2 even though the 'reference interval' continues to rise
in the population. So, when pathology and normality can overlap
significantly, is it appropriate to quote the reference interval?
I guess I'll have a good time justifying our decision when CPA next come
round!
Eric
Dr. Eric S. Kilpatrick
Consultant in Chemical Pathology
Hull Royal Infirmary
Anlaby Rd
Hull HU3 2JZ
Tel: 01482-607708
Fax: 01482-607725
----- Original Message -----
From: Martin Brian (RH8) R D and Exeter HC Tr
<[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 01, 2002 4:05 PM
Subject: ALT reference ranges
> Taking the opportunity of a major change in laboratory analyser (Vitros
950
> --> Roche Modular) we have swapped our main liver function test
transaminase
> from AST to ALT. With only a very small correlation to go on with our
> previous method, we decided to adopt the manufacturer's suggested
reference
> ranges as our 'norm' (Females 5 - 31, Males 12 - 41 U/L). These are
> identical or very close to those quoted by neighbouring laboratories.
> However, following the change, we have noted a substantial number of
mildly
> elevated ALT resuts in adult patients with otherwise normal LFTs. (This
was
> not evident when AST was the measured transaminase). Are our ranges
wrong?
> Or is the ALT indicating a local population of patients with mild liver
> damage ('retired, but drinks a lot')?. Any comments would be gratefully
> received.
>
> Brian Martin
>
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