Principles of clinical chemistry Flashcards
Why are clinical labs important?
Disease diagnosis, severity. Diagnosis is achieved via physical examination and then confirmed by lab diagnostic tests
What are the most requested samples?
Biological sample for urine and faces, venous blood
What is a qualitative sample?
What is a quantitative sample?
Number of something such as concentration or amount of metabolite.
What is plasma?
Blood with all cells removed.
What is serum?
Blood with all cells and coagulation proteins removed.
What is used to prevent coagulation?
EDTA
What colour is serum when RBC have ruptured?
Yellow due to haemolysis with the release of haem.
Orange/brown serum
Bilirubin present in blood, indication of jaundice
What is measured in a biological sample?
1) Concentrations/levels of metabolites
2) Presence of particular proteins
3) Enzyme activity
What should be considered in biological sample?
Ease of obtaining sample and location of target analyte.
What allows accurate interpretation of results?
Patient characteristics such as age, sex, menstrual cycle stage
What happens in sample transport failure?
Sample deterioration and may be a biohazard
What are the groups of laboratory tests?
Selective requesting: based on individual patient’s clinical situation
Screening test: searches for disease
What are the selective tests?
One-off tests: asks specific questions to support diagnosis
Biochemical profiles: plasma electrolyte and liver function test
Dynamic function test: measures response to external stimulus
What is a dynamic function test?
Measures response to external stimulus.
What is a biochemical profile?
Measures plasma electrolyte and liver function test.
What is arterial blood sampling?
Determines arterial blood gases; this is performed via heparinised syringe. The require rapid transport on ice.
What is the role of selective testing?
Confirm diagnosis and differential diagnosis, assess severity of disease, monitor progress of disease and see side effects.
How are test results interpreted?
Analytical variation: limitation of the test
Sensitivity: Detection limit
Specificity: How good the assay is at discriminating between analyte
What is biological variation?
Results are affected by physiological factors. It is compared to reference range.
What is analytical variation?
Limitations of the test, considering precision and accracy. Includudes sensitivity and specificity
What is sensitivity in analytical variation?
Detection limit
What is specificity in analytical variation?
How good the analyte is at discriminating between analyte and any contamination.
What are the core biochemical test?
Na+, K+, Cl– these are produced in hospitals and clinics.
What is the role of aminotransferase enzymes?
Synthesis of amino acids. Examples include aspartate aminotransferase (AST) and alanine aminotransferase (ALT). They are sensitive markers for liver damage.
What is prothrombin time (PT) ?
Measures time of extrinsic pathway; prolonged time is an indicator of liver disease