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What 4 things does an accurate chemical analysis depend on?
- proper collection
- perservation of sample
- processing of sample
- method of analysis
- *all are equally important*
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What is the idea time for lab measurements to be performed?
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Why are specimens preserved?
- 1. so the substance will not be altered
- 2. specimens collected in a timely sequence should be stored until they can be analyzed at the same time
- 3. samples retained or kept long enough to repeat if necessary
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What sample is most often used for chemical analysis?
- Serum
- *preferably fasting serum*
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What is the differance between serum and plasma?
- 1. Serum is liquid portion with fibrinogen and clotting factors removed.
- 2. Plasma is liquid portion of the circulating blood and it contains fibrinogen and clotting factors.
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What methods are used to preserve specimens?
- 1. Part of specimen collection- sodium fluoride is the preservative in the gray top tube.
- 2. We can refrigerate specimen, but must be brought to RT before testing.
- 3. Separating the cells from the serum & plasma (the gold tube is usually used for separation)
- 4. There are special requirements - ie. protect bilirubin from light.
- 5. Freeze serum or plasma
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What is the silicone barrier used for?
- To separate serum or plasma from cells.
- Usually gold top tubes are used, the jell in the bottom of tube is (thixotropic gel).
- 1. The jell prevents the shift of substances.
- 2. It also prevents glycolysis.
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What vacutainer is used to collect serum and why?
Gold top or red top tubes have no anticoagulant in the tubes.
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How is a gold top tube processed?
- 1. inverted 5 times- do not remove stopper, or centerfuge imediately after drawing
- 2. allow to clot upright- at least 30 mins. no more than 60 min.
- 3. centerfuge at least 15 min. within 1 hr. of collection
- 4. transfer to a labeled plastic screw cap vial
- 5. Refrig (cool) or freeze
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What are the precautions when handling blood?
- 1. gloves
- 2. open stopper carefully away from you
- 3. disinfect blood spills immediatly with 10% bleach or disinfectant
- 4. discard tubes and sharps in crush & leak proof container
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Hemolyzed serum
a clear red color to the serum or plasma
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Icteric or (hyperbilirubinemia, jundice)
brownish yellow, patient may have jaundice or hepetisis
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Lipemic
the serum or plasma is milky white
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Accuracy
- the true or actual size
- ex. bullseye
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Percision
repeatability, reproducablility
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Normal value
- average results of healthy individuals
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Batch or run
- Specimen analyzed at the same time.
- ex. a batach of cookies
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Standard
- Calibrator used to set machine values
- ex. alarm clock
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Control
- Checks accuracy
- Must fall within acceptable range before patient value reported
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Duplicate determination
One of the specimens in the batch is measured twice and it check precision
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Proficiency survey
- Specimens are sent to your lab
- You analyze samples and send the results.
- The agency will let you know how you did and how you compared to other labs
- *meap testing for labs*
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What does a quality control program include?
- 1. standards or calibrators
- 2. controls
- 3. duplicates
- 4. profenecy service
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What 4 things does the control check for?
- 1. machine or instrument
- 2. reagents, strips, test cards, and starting manual
- 3. operator
- 4. environment temp. and humidity
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What steps should follow if a control fall outside of the acceptable range?
- 1. document it ( in lab log)
- 2. check everything
- 3. retest the same control vial
- 4. retest new vial
- 5. recalirbrate the machine
- 6. call customer service
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What is great about fasting?
- reflects metabolic base line
- avoids lipema (which is fat in blood)
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Controls
- 1. Use universial precautions pooled serum/plasma, control may have human antigens.
- 2. Unopened exp. date, midnight, last day of month opened.
- ex. 2011-07 is July 31, 2007 at midnight
- 3. Results reported according to lot #
- 4. Keep QC results 2 years
- 5. CLIA wavied quality contrl testing according to manufacturers instruction. (clia has 3 levels of testing. waived, moderate and high)
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