LMP299Y1 Lecture Notes - Lecture 2: Anticoagulant, Fibrin, Sodium Oxalate
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Published on 19 Jan 2015
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LMP301 Lecture 2
Lab Tests and Their Interpretation
- introduction to laboratories
- testing process and variables that affect lab tests and their results
- interpreting disease and introduction to cases
- social and ethical issues
Lab Reimbursement in Ontario
- schedule of laboratory services is funded by the MOHLTC (Ontario Ministry of Health and Long-Term Care)
- lab areas generally divide into:
•clinical biochemistry
•hematology
•immunology (often part of biochemistry)
•microbiology (including virology and parasitology)
•anatomic pathology
- other tests are either not available or not considered by the government to be part of the standard of care
(either use insurance or pay out of pocket, depending on the test)
- in hospital laboratories – biochemistry and hematology labs usually have a STAT service and a Routine or
“Core” Laboratory
- large centres also have specialized lab testing
- large menus of testing are available in “full service labs”
- pediatric, etc. hospitals also have very specialized tests
Test Menu Considerations
- categories of test menus
•STAT tests
•routine tests
•specialty tests
- considerations for test availability
•turn-around time (TAT)
•cost control
•technical expertise (easy to perform vs. need years of experience)
•clinical need (physician’s office vs. intensive care unit)
- needs of the clients are going to depend on what you make available
- example of TAT in emergency rooms – need quick testing
Types of Markers (of disease)
- not everyone breaks them down in the same way
-physiological markers
•analytes which are monitored to assess normal function
•tightly controlled
•under normal physiological response, body will restore the balance
•body will attempt to restore the marker (sugar level, electrolytes, etc.) if too far off
•if too far off where the body can no longer compensate – may indicate disease
•injury or disease may alter the balance – body may or may not be able to compensate
•examples of markers – electrolytes, body gases, pH, glucose, protein
•these markers have ranges of levels (reference ranges) – outside that range, it often indicates
disease, etc.
-disease markers
•analytes which are monitored as an indicator of disease
•normally found in small amounts as by-product of metabolism
•not controlled – broken down or excreted as waste
•large amounts usually indicate problems/disease
•either too much occurring at once, or the body’s ability to repair it has been damaged
•injury or disease increases – eventually exceeds the body’s ability to clear the marker
•not to say that it does not appear normally – just very low amounts because the body often filters
•often the kidney clears it – dysfunction of the kidney usually causes
•examples of disease markers – urea, creatinine, enzymes, bilirubin, cardiac troponin
•the markers can be tested differently – usually numbers can generally fall into a range because
methods have been standardized
•some markers such as Troponin have not been standardized and therefore levels vary (normal
range depends on the test used)
Common Biochemistry Tests
- routine tests:
•electrolytes (sodium, potassium, chlorine, bicarbonate)
•urea and creatinine
•glucose
•calcium and phosphate
•total protein and albumin
•bilirubin, liver enzymes
- STAT tests
•electrolytes (sodium, potassium, chlorine, bicarbonate)
•urea and creatinine
•glucose
•blood gases
•salicylate, acetaminophen
•chorionic gonadotropin
•troponin
Patient Self-Testing and Point-of-Care (POC) Testing
- outside of lab testing – “near patient”, “near bedside” testing
- good for urgent, near patient testing
- hand-held, portable devices
- many routine chemistry assays
- fast result time, good for urgent situations
- good quality if used exactly as recommended
-home monitoring – urine glucose, urine HCG, blood glucose, etc. – “home cholesterol test”
- with home monitoring, the results are fast but unknown reliability (no quality control like there is in hospital)
-near-bedside testing – blood glucose, electrolytes, blood gases, etc.
- cons (POC testing) – high running cost, limited (or lacking) quality control, no legal barriers in acquiring
(assuming it has been approved – must be approved by the government in Canada)
- in hospital – POC testing occurs using instruments that have passed what the hospital required to be of
sufficient quality – very high quality and on sick patients
Specialty Tests
- done by specialized centers – not to say that they cannot be don’t on a routine of STAT basis
- not a very high demand, and usually no urgent decisions must be made based off them
- often also “specialty” because they are expensive and it is more cost efficient to do them in batches
- because they are often done in batches, often have to wait weeks or months even, until the testing is done