Clinical Biochemistry Flashcards
1
Q
Core Lab
A
- found at all hospitals
- operates 24/7
- highly automated
2
Q
Special Chemistry
A
- less frequent
- labour intensive
- doesnt need immediate results
3
Q
Point of care testing
A
- instruments located outside of chemistry laboratory such as ICU, ER etc
4
Q
Core lab tests
A
Electrolytes, blood gases, endocrine, lipids, proteins, glucose, tumour markers, vitamins, toxicology, ethanol, methanol, drug abuse, specific proteins etc
5
Q
Point of care testing tests
A
- blood glucose
- urinalysis
- blood gases
- electrolytes
- cardiac markers
- drug screens
6
Q
Why are tests ordered?
A
- Diagnosis
- Monitor progression of disease
- Monitor effectiveness of treatment
- Screening population for diseases
- To identify complications of treatment
- For predicting survivability, employability
- To check the accuracy of an unexpected data
- To conduct research
- To prevent malpractice
- For educating residents
- To assess nutritional status and health of an health individual
- Responding to total uncertainty
7
Q
Are cardiac markers and drug screens qualitative or quantitative?
A
qualitative tests
- can be recorded and reported
8
Q
Are urinalysis qualitative or quantitative?
A
can be qualitative, or quantitative
- hard copy of results generated
- possible to interface hospital LIS
9
Q
High specific marker
A
troponin t
- marker of myocardial infarction
- found in cardiac tissue
- released into bloodstream following cell death
10
Q
Non specific marker
A
low blood pH (acidosis)
- drugs
- respiratory problems
- renal problems
11
Q
Lab Tests
A
- Measuring an analyte as a Marker to distinguish health and disease
- Ideal Marker
- Absolutely specific for a specific disease
- Easily measurable
- Quantity reflective of severity of disease
- Early detection following onset of disease
- Not affected by other biological disturbances
12
Q
Blood analysis- source
A
- veins
- arteries
- skin puncture capillary blood
13
Q
Blood analysis- factors affecting choice of blood source and collection method
A
- analyte under investigation
- vascular status
- ease of collection
14
Q
Blood analysis- collection method
A
syringe, evacuated tube, additives, separator gel, and intravenous ilnes
15
Q
What are the most widely used tubes?
A
evacuated tubes
16
Q
Why are evacuated tubes mostly used?
A
- negative pressure facilitates collection
- sterile
- easy to use
- universally used colour coded rubber stoppers to denote tube type
- tubes can contain various anticoagulants
- tubes can have additives for specific tests
17
Q
Red tubes
A
- contain no anticoagulants or preservatives
- used for collecting serum
- 10/15 min is needed to allow blood to clot before centrifuging
- used for blood bank specimens and chemistry
18
Q
Gold and Tiger tubes
A
- contain a gel that forms a physical barrier between the serum and cells after centrifugation
- no additives present
- gel barrier can affect tests
19
Q
Grey tubes
A
- used for glucose measurement
- after blood collection, glucose concentration decreases significantly because of cellular metabolism
20
Q
What can the grey tube contain?
A
- sodium fluoride or potassium oxalate
- sodium iodoacetate
- NaF
- Iodoacetate inhibits glucose-3-phosphate dehydrogenase
21
Q
Green tubes
A
- contain either Na, K, or lithium salt of heparin
- used anticoagulant for chemistry test
- effect size and integrity of cellular blood components and not recommended for hematology studies
- heparin accelerates action of antithrombin which inhibits thrombin so blood doesnt clot
22
Q
Lavender tubes
A
- contain K salt of ethylenediaminetetraacetic acid (EDTA), which chelates calcium (essential for clot formation) and inhibits coagulation
- Used for hematology, and some chemistries
- Cannot be used for K or Ca tests
23
Q
Blue tubes
A
- contain sodium citrate which chelates calcium and inhibits coagulation
- used for coagulation studies because it is easily reversible
24
Q
Brown and Royal blue tests
A
- specifically for trace metal studies
- brown top are used for lead analysis
- royal blue are used for other trace elements studies
25
Test results: variations, errors and interferences
- Clinical variations within an individual and between individuals
- Analytical variations-no test is perfect. All tests have some degree of variations for repeated measurements of the same sample.
- The final test result is affected by factors that occur
- Pre-analytically
- At the time of the test
- After the test is completed
26
Steps in obtaining a lab test
- Test is requested by physician and ordered on the computer. Barcode is generated
- Specimen is collected
- Specimen and order are transported to the lab
- The specimen is accessioned in the lab
- The specimen is processed
- The specimen is analyzed
- The results are reviewed and verified by an technologists
- The results are released to the patient’s record
27
Analytical results vary: inter-individual variation
age, sex, race, genetics, long term health status
28
Analytical results vary:intra--individual variation
Diet, Exercise, Drugs, Sleep pattern, Posture, Time of venipuncture, and time tourniquet is applied
29
Analytical results vary: pre analytic variation
- Transport
- Exposure to UV light
- Standing time before separation of cells
- Centrifugation time
- Storage conditions
30
Analytical Variation
- Random errors
| - Systematic errors
31
Post-analytical
- Transcriptions errors
| - Results reported to wrong patient
32
Pre analytic errors
- Collection
- Was the right tube used?
- Was venipuncture performed correctly?
- Was the specimen properly stored?
- Identification
- Was the blood collected from the correct patient?
- Was the blood correctly labeled?
- Patient name, ID, date, time of collection, phlebotomist
33
Specimen identification
- One of the common sources of erroneous lab results is misidentified specimens
- The lab is required to have a clear and rational policy for identifying specimens, and handling misidentified specimens
- Retrievable versus irretrievable
- Retrievable refers to collection of easily obtained substances – eg urine (non-invasive, can get again)
- Irretrievable might be pediatric CSF or even blood (cannot get again)
34
Prolonged Venous Stasis - pre-analytical errors
- Small molecules, water and ions are forced out blood vessels and larger molecules are concentrated
- Increases Total Protein, proteins, iron, cholesterol, bilirubin
- Decreases potassium
35
Supine vs sitting or standing
- Going from lying (supine) to upright reduces total blood volume by about 700 ml
36
The following may decrease by 5-15% in the supine patient:
- Total protein
- Albumin
- Lipids
- Iron
- Calcium
- Enzymes
37
Hemolysis
- rupture of RBC
- can be due to improper collection
- end result is dumping cellular contents into blood
- mild dilution effect in some analytes
- significant increase in potassium, magnesium and phosphorous
38
Interferences are
hemolysis and lipemia
39
Hemolysis interference
- The release of hemoglobin into blood can affect the reactions comprising specific tests
- Causes serum or plasma to be red and can affect tests that are colorimetric
40
Lipemia
lots of fats and lots of protein
41
Lipemia interference
- Causes serum or plasma to be become turbid.
- This can effect colorimetric and turbidimetric based tests
- Also can cause a dilution effect. Fats and proteins are large and displace water in plasma. Can give falsely low results especially for Na
