Overview of the Laboratory Analytical Process Flashcards
How many medical decisions are based on laboratory results?
75-80%
What is the most common fluid submitted for analysis?
Blood
What is the 2nd most common fluid submitted?
urine
What are qualitative tests? How are results reported?
generally “screening” procedures. Reported as positive or negative. Ex: pregnancy test
What are quantitative tests? How are results reported
measures the amount of substance present. Reported in units of measure. Methods tend to be more technically demanding. Ex: Cholesterol level
What is semi-quanitative testing?
Not as accurate as quantitative testing, but can provide an indication of approximate concentration of a substance. Ex. UA reagent strip: glucose, protein, blood, etc
What do screening tests determine?
The presence or absence of a disease or condition.
Are screening test qualitative or quantitative?
They can be both.
What are confirmatory tests?
confirms the accuracy of a screening test by ruling out false pos or false neg results. Uses a different methodology than a screening test.
Screening tests require…
a high SENSITIVITY to eliminate FALSE NEG
Confirmatory tests require…
a high SPECIFICITY to eliminate FALSE POS
How to labs define a test as abnormal or normal?
They use a reference range.
How are references ranges determined?
by each laboratory (institution).
How are reference ranges established?
performing tests on groups of healthy people to determine expected results for a healthy population. Should reflect a GAUSSIAN distribution.
How is the reference range statistically calculated?
The mean, +/- two standard deviations. They should include about 95% of values from the healthy individuals tested.
A value that falls outside of the reference range is called?
Abnormal and suggests the presence of disease
What is a value “just below” or “just above” the range is called?
Gray zone. Basically, what is normal for one person may be abnormal for another. Healthy person may have abnormal value. Individual who is not healthy may have normal results.
What are the three phase of the testing process?
pre-analytical, analytical, post-analytical.
Describe the Pre-analytical phase
includes all aspects of specimen procurement that could affect the integrity of the test sample
What aspects of the pre-analytical phase could be affected?
ordering correct test, patient prep, specimen collection, transport to lab, processing of specimen before analysis.
What is the analytical phase?
encompasses the actual testing process.
What aspects of the analytical phase could be affected?
reagents, type of water used, instruments, type of glassware, individual technique, do the test results make sense?
What is the post-analytical phase?
Reporting lab data to healthcare provider
What aspects of the post analytical phase could be affected?
recording or reporting tests, calculation of results, critical patient values, do patient values correlate with previous results?
What should the final test results reflect?
all the factors encountered during all phases of the analytical process
What are the most common source of invalid test results and the most diffucult to account for?
pre-anaylitcal phase mistakes
How does the lab try to reduce errors?
protocols, written instructions for patient and health care providers.
What is quality assurance?
the lab must provide accurate and precise testing results. QA procedures are used to control factors that could affect patients results.
What does quality assurance consist of?
Written policy and documented actions
What written lab procedures must be followed?
Clinical and Laboratory Standards Institute format. (see slide 28 and 29 for examples)
