As some of you may well know there is an imminent change in standardisation
of
growth hormone assays on the way. The current GH Standard 80/505 is due to
be
replaced by IS 98/574 and there is a general wish among the worldwide
endocrine
community that GH be reported in mass units, i.e. ng/ml, rather than the
current
UK practice of mU/L. (see Clin Endocrinol (2004)60:538-539.) In the
beginning
this will necessitate the use of conversion factors. Those of us who use the
Nichols Advantage system have less than 6 weeks to make the change. I am
unaware of what DPC, the most-commonly used assay, is recommending. Most GH
requests form part of a dynamic function test either stimulation in
response to
a pharmacological challenge or suppression in response to a glucose load or
to
monitor therapy in acromegalic patients. Currently we use fairly standard
cut-off levels for these challenge tests
e.g. < 0.5 mU/L in response to glucose to rule out acromegaly, and > 20
mU/L as
evidence of adequate GH reserve. No doubt we will have to revise these
figures
in light of both the new standard and the new reporting units.
Has anyone out there already tackled these problems e.g. are the conversion
factor(s) constant throughout the range of GH values? Has anyone decided on
new
cut-off levels?
I know that UKNEQAS are working hard on the issue but I wonder if general
guidelines ought not to be discussed by those with experience and knowledge
of
the anticipated problems.
I also wonder how well informed are our clinicians of the imminent changes
and
will we be required to report in the two units (reconverted to 80/505 from
98/574) for a length of time.
Michael Diver
Senior Lecturer
RLUH
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