Principles Of Clinical Chemistry Flashcards
What do clinicians use to confirm the findings of of their physical examinations
Lab diagnostic tests
What are the uses of clinical laboratory
Diagnosis and in the monitoring of the treatment
Screening for disease/ assessing the prognosis
Research into the biochemical basis of disease
Clinical trials of new drugs
What are the most requested biological samples
Urine, faeces
Venous blood (serum or plasma) or arterial blood
Others commonly requested:
- CSF, sputum and saliva, tissue biopsy or cells. Aspirates (pleura fluid, synovial fluid)
Centrifugation is used to separate blood into plasma and serum. What is the difference between plasma and serum
Plasma with all cells removed
Serum = blood with all cells and coagulation proteins removed
Permanent characteristics that must be documented ( allows for accurate interpretation of results)
-age
- sex
- pregnancy
- stage of menstrual cycle
- body size
- ethnic group
- genetic variant
- non - specific illness
- medication
- normal diet/ drink
Other parameters that can be controlled
Recent exercise
Posture during sample retrieval
Interval since last meal
Interval since last dose of drug
Time of day
What can be measured in biological samples as way to pick up any disease
Concentrations or amounts of metabolites: glucose or amino acids
Presence of particular proteins such as troponins in MI
Enzyme activity = alkaline phosphatase for liver disease
What groups can biochemical tests be divided into
1) selective requesting = carried out based on an individuals patient clinical situation. The tests are divided into core and specialised
2) screening tests = used to search for disease without there being any necessary indication that disease is present
Examples of selective testing
One off tests = designed to answer specific questions - does the patient have increased blood urea/glucose concentration. Used to support the diagnosis
Biochemical profiles: information on disease status can be obtained by analysing multiple constituents rather than one. Plasma electrolytes (Na+, K+, Cl- and bicarbonate, urea) liver function tests (serum bilirubin, ALT, AST)
Dynamic function tests - measure the body’s response to external stimulus eg oral glucose tolerance test (to assess glucose homeostasis)
What is the purpose of selective testing
To confirm diagnosis
To aid differential diagnosis
To assess severity of disease
To monitor the progress of disease
To detect complications or side effects
To monitor therapeutic intervention
Will results affect diagnosis? Will results affect treatment? Will results affect prognosis? If answer is NO then test is not appropriate for the patient
What types of variation can occur
1 ) analytical variation = relates to the limitations of the test itself (precision and accuracy of test)
2) biological variation = discrimination between the normal and abnormal results are affected by a variety of physiological factors
Eg sex, age, diet, drugs, pregnancy, medical history and stress
What is sensitivity
how little of the analyte can the method detect (detection limit)
What is specificity
Specificity = how good is the assay at discriminating between the required analyte and substances which interfere with the assay
Types of jaundice
- haemolytic
- cholestatic
- hepatocellular
Cause of acute liver disease
Poisoning
Hepatic failure
