42. Pre-analytical considerations of the hormone tests.

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Revision as of 14:56, 30 May 2024 by Nikolas (talk | contribs) (Created page with "* 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 – influen...")
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  • 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