1. All you wanted to know about laboratory tests, but were afraid to ask By Dietmar Stöckl STT Consulting - 3 - The informed patient meeting the laboratory director Metrology Measurand 2

2. All you wanted to know about laboratory tests -3- 2 Measurand Without your wife? She got migraine from all that stuff! She said, today would be stimulating...... whatever she meant by that...

3. All you wanted to know about laboratory tests -3- 3 Measurand S-[“unspecified”] glycosylation mixture of [“intact”] TSH; arbitrary amount of substance concentration x mIU/L Assay requirement Equimolar measurement Thyroid stimulating hormone No showers?

4. All you wanted to know about laboratory tests -3- 4 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?

5. All you wanted to know about laboratory tests -3- 5 Measurand TSH I type,... the profession has some homework to do. Will they ever agree on one thing?

6. All you wanted to know about laboratory tests -3- 6 The next visit Accuracy; trueness; precision; total-, systematic-, random error More "thunderstorms"

7. All you wanted to know about laboratory tests -3- 7 Resources The term human thyroid stimulating hormone (hTSH) describes a glycosylation mixture of a heterodimeric glycoprotein hormone formed by noncovalently bound  - and  -subunits. The  -subunit has 92 amino acids (common to all human glycoprotein hormones) and 2 N-glycosylation sites at Asn-52 and Asn-78. The  -subunit has 118 amino acids and 1 N- glycosylation 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 NH 2 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

8. All you wanted to know about laboratory tests -3- 8 Resources Structure of hCG, another glycoprotein hormone http://www.chem.gla.ac.uk/research/groups/protein/glyco/GPH.html

9. All you wanted to know about laboratory tests -3- 9 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.