Laboratory Methods and Quality Assurance Flashcards
List and describe three sources of laboratory error.
- Pre-analytical factors: Occur prior to sample analysis, often before the sample gets to the lab. May relate to the patient (Age, breed, excitement), sample collection and handling, or shipping conditions
- Analytical factors:
- Post-analytical factors:
List three patient variables that can be seen in serum that may serve as pre-analytical factors of laboratory error.
- Lipemia
- Hemolysis
- Icterus
_____ often occurs after eating a fat-containing meal and causes circulating triglycerides. What does this cause the serum or plasma to look like?
- Lipemia
- Milky
______ is when red blood cells rupture, releasing hemoglobin. What does this cause plasma or serum to look like? What can cause it?
- Hemolysis
- Causes red discoloration
- Due to sample collection from difficult venipuncture, incorrect needle size, excessive pressure on the syringe, or rough transfer of the sample to the collection tube
_____ is increased bilirubin concentration. What does this cause the serum or plasma to look like? What might it be due to?
- Icterus
- Yellow discoloration
- Pathogenic hemolysis or liver disease
How might drugs or other treatments serve as a pre-analytical factor that can cause laboratory error?
They can cause physiological change in the patient or interfere with the analytical procedure. For example, corticosteroids cause increased alkaline phosphatase and bromide, an anti-seizure medication, can interfere with chloride determination.
Are inaccurate collection procedures, such as inaccurate sample labeling, using the wrong collection tube, filling the tube incorrectly, or not gently mixing as indicated, pre-analytical, analytical, or post-analytical causes of laboratory error?
Pre-analytical
For most species, samples for complete blood counts should be collected in _____ anticoagulant, which is in the ____ top tubes.
- EDTA
- Purple
True or False: EDTA anti coagulated blood and blood smears can be refrigerated before analysis.
-False, blood smears cannot be refrigerated
Incorrect processing, storage, or shipping of samples to the laboratory are all examples of _________ laboratory error.
Pre-analytical
______ factors are factors that affect assay performance. Give four examples.
- Analytical
1. Analyzer and Equipment
2. Test methodology and components
3. Quality Control Procedures
4. Operating and Maintenance Procedures
_____ is the agreement between a lab result and its “true” value which is assessed by comparing a patient result with a result from a control sample with a known true value.
Accuracy
True or False: A test result must be both accurate and precise for it to be useful.
True
______ is the agreement between replicate measurements, it is repeatable
Precision
True or False: If you run the same sample through the same analyzer several times, the result must be the same each time to be considered precise and accurate.
False, some variation is acceptable
When a new test is developed, it undergoes a variety of ______ _____ to make sure it accurately and precisely measures the desired analyze. The new test is compared to a reference method, called the _____ _____, to make sure the new procedure produces accurate results for normal and sick animals.
- Validation procedures
- Gold standard
_____ _____ are created by sampling animals from a healthy population and are specific for each species, instrument, and methodology. The results are used to determine if data from a test is normally distributed. What does it mean if a patient has a lab result that is outside the value?
- Reference Intervals
- May mean increased likelihood of disease, high probability of a specific disease, or treat may be needed
True or False: Normal, healthy animals will never have a test result outside the reference interval.
False, some normal animals will have test results outside the reference interval
Quality control and Reference Intervals are both examples of things that are _____ factors of laboratory error.
Analytical
A _____ ____ program is designed to detect lab errors before results are sent to the clinician. Describe SOP, Calibrators, and controls that are a part of this.
- Quality Control
- SOP: Step by step directions for performing a test and operating the instrument so that the test is run the same way each time
- Calibrators: reference materials periodically measured on the instrument to make sure it is performing correctly
- Controls: Contain a known quantity of the analyze being measured.
______ _____ factors, such as accurate entry of data into the medical record, affect your results after the test is run.
Post-analytical
Define sensitivity of a test.
- Animals with the disease that have a positive test result
- True positive /(true positive + false negative)
Define specificity of a test.
- Animals without the disease that have a negative test result.
- True negative / (True negative + False positive)
A screening test should be highly _____, whereas a confirmatory test should be highly ______. Describe the reason for each
- Sensitive (screening tests should be sensitive so you don’t miss patients that might have the disease)
- Specific (confirmatory tests should be specific since you are basing treatment decisions on them)
