View source for 42. Pre-analytical considerations of the hormone tests.

* Measured by serum in plain tube (red) or gel tube (yellow)
* Small peptide hormones
** Unstable, transported quickly and on ice
** TRH
** Renin
* Amino acid derivatives
** T3, T4
*** Only free fraction is measured
*** Protein binding influences measurement
** Adrenalin
* Steroids
** Cortisol
** Aldosterone
** Sex hormones
** Both fractions are measured
*** Binding protein should also be measured
* Biological variation
** GH – pulsatile release
** Cortisol – influences by stress, diurnal rhythm
** Should be measured in the morning
** Log-linear relationship – small change in TRH can cause significant change in TSH
* Analytical variations
** Measured by immunoassays
** Immunoassay interference
*** Heterophilic antibodies – low affinity antibodies
*** Anti-animal antibodies
*** Autoantibodies
*** Antibodies from treatment
*** Rheumatoid factor
** Matrix effect
*** High level of molecules in plasma -> molecules can cover epitopes of analyte -> underestimate level of analyte
** High-dose hook effect
*** More analyte than capture antibody -> analyte binds to detection antibody without being captured -> detection antibodies depleted -> fewer captured analytes can be labelled -> false negative result

[[Category:Clinical Biochemistry (POTE course)]]