Dear Brian:
For our in-house reference range study involving 98 healthy volunteers, the
97.5th percentile for ALT was 53 U/L, and the highest value was 69. The mean
and median, however, were 18 and 14, respectively. Because the distribution
of ALT measurements in healthy individuals is severely skewed,
parametrically-determined reference intervals underestimate the upper limit
of normal. I don't know whether Roche, or your neighboring laboratories,
used the mean +/- 2 SD to establish their ALT reference ranges, but this
could be one reason that you're seeing an unexpectedly large number of
mildly elevated results.
Kind regards,
Roger
Roger L. Bertholf, Ph.D.
Associate Professor of Pathology
Director of Clincal Chemistry & Toxicology
University of Florida Health Science Center/Jacksonville
> -----Original Message-----
> From: Martin Brian (RH8) R D and Exeter HC Tr
> [mailto:[log in to unmask]]
> Sent: Wednesday, May 01, 2002 11:05 AM
> To: [log in to unmask]
> 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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