Lecture 1 - Introduction Flashcards
What is Clinical Biochemistry
Clinical Biochemistry is the clinical science of examining blood and other fluids to diagnose
and monitor disease and inform therapy.
What is Laboratory Medicine
Laboratory Medicine includes Clinical Biochemistry and other laboratory based scientific disciplines such as immunology, microbiology, haematology and genetics that underpin the diagnosis, management and cure of diseases and other medical conditions.
Steps in the Investigation of a Patient
Patient History
Physical Examination
Laboratory Tests
Imaging Techniques
Diagnosis
Therapy
Evaluation
How do we identify abnormal biochemistry?
• ‘The Normal Range’ Defines the values of a biochemical test found in healthy subjects against which patient values
can be compared.
• Artificial concept - no clear boundaries exist.
• Preferred term is ‘Reference Interval’
Factors effecting reference range
- age
- gender
- diet
- pregnancy
- weight
- method
- time of day, month, year
How biochemical results are expressed
Analytes - molar units
Enzymes - activity in blood
Hormones - concentrations
Proteins - concentration
Blood gases - pressure
The outcome of diagnostic test table
Test utility
• Sensitivity: patients with disease correctly identified by the test.
• Specificity: people without disease correctly identified by the test.
• Prevalence: pre-test probability of disease (How common)
Types of clinical laboratories
- core lab facility
- special chemistry
- point of care testing (POCT)
Core lab facility
- high volume tests, often require quick results
- found in most big hospitals
- operates 24h day 7 days a week to provide the essential most requested tests
- Highly automated environment
- Instruments with Multi-analyte capabilities
What is special chemistry labs
- less busy
- less frequently ordered tests
- labour intensive and often manual methods generally, result not required immediately
- more training required
Point of Care Testing
- urgent importance
- Instruments located outside of chemistry laboratory such as cardiac care unit (CCU), ICU or GP surgeries
Core lab instrumentation
- bar coded test tube
- pipetting, mixing and measuring is auto
Purpose of testing
- diagnosis
- monitoring
- prognosis (information about the likely outcome)
- screening (detection of subclinical disease)
- research
Defining the reference range *
- screen a group of healthy people in a population
- plot results (y: frequency of occurrence, x: test value)
- normal distribution shown
- 2.5% margin
Factors effecting reference range - blood concentration
Adult male: 13.5-17.5
Adult female: 11.5-15.5
Child (1-puberty): 11.0-13.5
Baby (3 months): 9.5-12.5
Newborn: 15-21
What are some core lab tests
- electrolytes
- blood gases
- endocrine
- lipids
- proteins
- glucose
- tumour markers
- vitamins and minerals
- toxicology
What is random access
Can perform specific tests on a specific sample
What happened once results are verified
They can be broadcast (sent out)
Special chemistry - electrophoresis
- used to sedate serum proteins into 5 distinct bands
- separate lipoproteins into 4 bands
- often use to separate isoforms of enzymes
Special chemistry - HPLC
- Measure vitamins and haemoglobin variants
Special chemistry - infrared spectroscopy
- analyse components of kidney stones
Special chemistry - chromatography-mass spectroscopy
- quantitative drugs measurements
Issues with point of care testing
- who is going to take the test, history
- who is calibrating machines
- are the poct instruments standardised with same test done with hospital instruments
Life of human biological sample
- Informed consent contract
- Sample collection
- Sample transport
- Tests and analysis
- Sample storage
- Sample destruction
Blood composition - plasma
- 55% of total volume of whole blood
- contains proteins, sugars, vitamins, minerals, lipids, lipoproteins, clotting factors
- 95% of plasma is water
What is serum
When blood is centrifuged the fluid portion
