Clinical Biochemistry 1 Flashcards
Define clinical biochemistry.
Clinical biochemistry = clinical analysis of bodily fluids for diagnosis, therapy and prevention of diseases.
Which sample tubes can be used for haematology?
Plain tube/serum - cannot use for fibrinogen but must use for bile acids, haptoglobin and protein electrophoresis.
Heparin tube
Oxf tube - used to measure glucose.
What biological factors affect results?
Inter-individual = inherent differences between groups of animals due to effects of species/bred/age/sex.
Intra-individual = transient differences in the same animal due to diet/excitement/reproductive status/drugs/method of blood sampling.
What are the most important pre-analytical factors?
Haemolysed, lipaemic or icteric plasma
Wrong anticoagulant (EDTA contamination) or non-sterile container
Transportation/storage of sample
Effects of medications
Describe lipaemia and the effect it has on a blood sample.
Lipaemia = turbid or milky serum/plasma
Increases or decreases values of some compounds, due to presence of extra lipid fractions and turbidity caused by lipids.
Interferes with light transmission (spectrophotometric assays).
What causes physiological and pathological lipaemia?
Physiological = post-prandial (need for fasted samples).
Pathological = endocrinopathies e.g. diabetes, hyperthyroidism.
Describe haemolysis and the effect it has on a blood sample.
Haemolysis = red-coloured serum/plasma due to free haemoglobin/myoglobin.
Increases or decreases values of some compounds due to concentration in RBCs.
Interferes with determinations by colour interface (spectrophotometric assays), chemical interactions and haematology.
Describe icterus and the effect it has on a blood sample.
Icterus (jaundice) = yellow serum/plasma due to increased bilirubin.
Does not interfere with haematology.
What is spectrophotometry?
Light source passes light through sample and based on how much light of a particular wavelength is absorbed, we can calculate the concentration of the compound of interest (e.g. urea).
What is Beer’s Law?
Spectrophotometry
A = abc
A - absorbance
a - constant
b - light pathway distance through cuvette
c - concentration of substance of interest
How can we prevent haemolysis?
Pay attention to sampling technique.
Avoid sample processing delays.
Separate plasma/serum from sample.
Refrigerate separated sample.
Name the two types of liver enzymes and what they indicate in liver disease.
Hepatocellular damage/leakage enzymes (ALT, AST (GLDH)) - increased levels indicate liver damage.
Cholestatic enzymes (ALP, GGT) - increased levels indicate blockage of bile flow.
What are the 3 main causes of increased bilirubin levels?
Pre-hepatic (increased RBC breakdown)
Hepatic (decreased bilirubin processing)
Post-hepatic (decreased bilirubin excretion)
What are the 3 main reasons for increased bile acid levels?
Decreased hepatic function
Decreased bile flow (cholestasis)
Portosystemic shunt
What is the bile acid stimulation test?
Fast overnight - Take a fasted sample into plain tube - Feed - Collect blood into plain tube 2 hours post-feeding.
