Transcript STT AllYouWanted 03 - STT

All you wanted to know about
laboratory tests, but were afraid to ask
The informed patient
meeting the laboratory director
Metrology
Measurand 2
By Dietmar Stöckl
STT Consulting
-3-
Measurand
Without your wife?
... whatever she
meant by that ...
She got migraine from all
that stuff!
She said, today would be
stimulating ...
All you wanted to know about laboratory tests -3-
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Measurand
Thyroid
stimulating
hormone
S-[“unspecified”] glycosylation mixture
of [“intact”] TSH; arbitrary amount of
substance concentration x mIU/L
Assay requirement
Equimolar measurement
No showers?
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Measurand TSH
Company-specific?
Some clinical chemists argue:
"The definition of the measurand includes the measurement
procedure with the prescribed use of a particular antibody"
Define TSH's by epitope used for measurement?
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Measurand TSH
I type, ... the profession has some
homework to do.
Will they ever agree
on one thing?
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The next visit
More "thunderstorms"
Accuracy; trueness; precision;
total-, systematic-, random error
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Resources
The term human thyroid stimulating hormone (hTSH) describes a
glycosylation mixture of a heterodimeric glycoprotein hormone formed by
noncovalently bound a- and b-subunits. The a-subunit has 92 amino acids
(common to all human glycoprotein hormones) and 2 N-glycosylation sites
at Asn-52 and Asn-78. The b-subunit has 118 amino acids and 1 Nglycosylation site at Asn-23. The carbohydrate chains constitute 15–25%
of its weight and have a high degree of heterogeneity. hTSH, purified from
the cadaver pituitary, has been shown to be heterogeneous at the NH2
terminus of each subunit due to variable terminal truncation of both subunit
polypeptide chains occurring physiologically or during purification.
Szkudlinski MW, Fremont V, Ronin C, Weintraub BD. Thyroid-stimulating
hormone and thyroid-stimulating hormone receptor structure-function
relationships. Physiol Rev 2002;82:473-502.
http://physrev.physiology.org/cgi/content/full/82/2/473
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Resources
Structure of hCG,
another glycoprotein hormone
http://www.chem.gla.ac.uk/research/groups/protein/glyco/GPH.html
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Resources
Recommended reading
Ekins R. Immunoassay standardization. Scand J
Clin Lab Invest 1991;51(Suppl 205):33–46.
Thienpont LM, Van Uytfanghe K, De Leenheer AP.
Reference measurement systems in clinical
chemistry [Review]. Clin Chim Acta 2002;323:73-87.
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