12. Laboratory analysis of plasma proteins
Plasma proteins
- Total protein
- Normal serum level 66 - 83 g/L
- Normal urine level < 0,1 g/L
- Biuret test (copper forms purple complex with proteins in alkaline solution)
- Colour intensity proportional to protein concentration – photometry
- Albumin
- Normal serum level 35 - 53 g/L
- Albumin forms green complex with BCG at pH 4,1
- Photometry
- Specific proteins
- Measurement based on immunogenicity – use of monoclonal or polyclonal antibodies
- Immunoassay – biochemical test measuring concentration of protein by using antibody
- Enzyme immunoassay (EIA)
- Enzyme-linked immunosorbent assay (ELISA)
- Radioimmunoassay (RIA)
- Fluorescence
- Proteins
- Microalbumin (high sensitivity albumin measurement)
- Hormones
- Tumour markers
- Drugs
- B12
- Folic acid
- Transferrin
- Ferritin
- EPO
- HCG
- Troponin
- Procalcitonin
- Separation techniques
- Chromatography
- Electrophoresis – sample added to gel -> electric field applied -> molecules separated by electric charge -> stained to make charged molecules visible
- Qualitative, semi-quantitative!
- Serum, not plasma (fibrinogen forms a band)
- Serum electrophoresis – monoclonal paraproteins
- CSF electrophoresis – multiple sclerosis
- Haemoglobin electrophoresis – haemoglobinopathies
- Lipid electrophoresis – dyslipidaemias
- Urine electrophoresis – Bence-Jones protein
Serum electrophoresis
- Serum electrophoresis
- Prealbumin=transthyretin
- Albumin
- Alpha-1 band
- alpha1-antitrypsin
- alpha1-acid glycoprotein (AGP)
- alpha1-microglobulin
- Alpha-2 band
- Haptoglobin
- alpha2-macroglobulin
- Caeruloplasmin
- Beta band
- Transferrin
- Beta2-microglobulin
- Complement factors
- Between beta and gamma
- Gamma band