Re: A query for ROCHE users regarding FT4 reference
ranges
Whatever the outcome of this query, any investigation into FT4
reference ranges would be additionally useful if it were also to
provide information regarding a. the methodology used eg
labelled analogue/solid phase antibody or solid phased
analogue/labelled antibody; b the nature of the analogue; c. the
method used to standardize (calibrate) the assay (ie an
"absolute" method, e.g. dialysis + RIA of dialysates or
"comparative" method e.g. using sera of supposedly known
FT4 content); the buffers used (if any) as serum diluents.
The original dialysis +RIA method developed by Sheila Ellis and
myself in the early 1970s yielded a reference range of 7.5
- 17.0 pg/ml (9.7 - 21.9 pmol/L), but the number of normal subjects of
both sexes was small and included pregnant subjects whose values was
later shown to tend to fall.
In a later study using the first of the direct FT4
immunoassays that my colleagues had developed (reported in 1979), the
range observed in 100 normal women was 9.8 - 22.4 pmol/L (
mean 15.4 pmol/L , SEM 0.32 pmol/L ); the mean in
(56) normal pregnant women in the first half of pregnancy was 14.4
pmol/L, SEM 0.4 pmol/L and- in (45) normal pregnant women in the
second half of pregnancy - the mean was 12.2 pmol/L, SEM 0.33
pmol/L . (Unfortunately I don't have the full experimental data
nor a full statistical analysis to hand at the moment, but the fall in
late pregnancy appears significant.)
The methodology used in these studies was the two-step assay and
did not incur the problems that affect analogue-based methods,
particularly the labelled analogue methods originally introduced by
Amersham (a method which we had considered but had been unable to
develop because of our inability to identify a satisfactory
analogue). I therefore believe these values are likely to be
reliable.
Roche use the solid phased analogue/labelled antibody
originally developed by my colleagues and myself and which we had
found to be accurate , but I don't know the nature of the analogue
presently used by Roche.
Note that some of the commercial methods on the market were
demonstrably invalid, but it's a long time since I've been involved in
this field and I am therefore unaware of any recent authoritative
studies that relate to this issue. Nevertheless caution is required
concerning what a methodology claimed to assay FT4 is actually
measuring.
Roger Ekins
Dear Roche users,
In order to check whether or not we are in-line
with national practice, please could anyone who is NOT using the Roche
kit insert recommended reference range for FT4 (12-22 pmol/L) email me
with their reference range for FT4, and the source of data from which
the reference range was derived.
Thank you,
Jinny Jeffery,
Clinical Scientist, Derriford Combined Laboratory,
Derriford Hospital, Plymouth, PL6 8DH.
------ACB discussion List
Information-------- This is an open discussion list for the academic
and clinical community working in clinical biochemistry. Please note,
archived messages are public and can be viewed via the internet. Views
expressed are those of the individual and they are responsible for all
message content. ACB Web Site http://www.acb.org.uk List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List
Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
--
Prof Roger Ekins, PhD DSc FRS
Windeyer Institute
University College London
London W1T 4JF
Phone +44 20 7679 9410
Fax +44 20 7679 9407
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical
community working in clinical biochemistry.
Please note, archived messages are public and can be viewed
via the internet. Views expressed are those of the individual and
they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
