Lecture 11a - Quality Part 1 Flashcards
What are the three phases of the total testing process?
- Pre-analytical
- Analytical
- Post-analytical
Which analytical phase is most likely to contain human error?
Pre-analytical Phase
What is the Pre-Analytical Phase?
The “prior to testing” phase.
What are some examples the pre-analytical phase?
Test ordering, specimen collection, sample labeling, checking patient identifiers.
What is the analytical phase consist of?
The “testing of the sample” phase.
Which phase in the total testing process has the least amount for potential human error?
Analytical Phase
What is the post-analytical phase consist of?
The “after testing is complete” phase.
Define Quality Assurance
Policies, procedures, and practices necessary to make sure that a laboratory’s results are reliable.
What is a QA program?
A plan to carry out policies and practices necessary to comply with QA standards set by accreditation agencies.
What is a Delta Check?
The difference between a patient’s current laboratory result and consecutive previous results that exceeds a specified cutoff value.
What is proficiency testing?
A sample is provided and the test is performed using the same method and procedure that is used for a patient. The results are submitted back to the agency, and the results are reviewed and communicated back. (CLIA requirement)
What is quality control?
Detecting and correcting errors; alerts analyst when there may be a problem with a testing procedure. Makes sure results are highest quality and most accurate.
What is internal QC (statistical)
Evaluates the DAILY precision of an assay.
What is External QC?
Evaluates the accuracy of assay measurements; requires submission of internal QC results and specified control specimens (ex: proficiency testing).
What are important characteristics to note when handling QC?
- Both levels are used.
- Make sure new lots are addressed
- Expiration date (open/expire dates)
How often must two levels of QC be ran?
Daily; for automatic analyzers bi-levels controls can be ran once every 8 hours.
Why would QC be out of range?
Errors in equipment, reagents, or individual technique.
What is a systematic QC error?
Caused by the same factor regularly producing reproducible error in one direction from the true value.
Ex: instrument calibrated incorrectly
What is a random QC error?
Caused by an accident that can be difficult to identify.
Ex: inaccurate pipetting
Define accuracy.
The closeness of the result obtained to the true or actual value.
Assessed using a “T-Test” - compares value of sample 1 on analyzer A vs. value of sample 1 on analyzer B.
Define precision
Repeatability, or reproducibility, in obtaining the same value in subsequent tests on the same sample.
Determine if this is accurate, precise, neither, or both.
Precise, but NOT accurate.
Determine if this is accurate, precise, neither, or both.
Accurate, but NOT precise.
Determine if this is accurate, precise, neither, or both.
Neither precise, nor accurate.
Determine if this is accurate, precise, neither, or both.
Precise AND Accurate
How is accuracy ensured in the clinical lab?
Standardized procedures, statistically valid comparisons of new methods with established reference methods, the use of controls, and participation in proficiency testing.
How is precision ensured in the lab?
Proper inclusion of standards/reference samples, statistically valid replicate determinations of a single sample, duplicate determinations of sufficient numbers of unknown samples, and day-to-day and between-run precision assessed by inclusion of control specimens.
Define what a standard is.
A highly purified substance of a known concentration purchased from a manufacturer.
What is a benefit of using standards?
- The best way to measure accuracy
2. Used to establish reference points to construct graphs or to calculate a test result
What is the difference between standards and QC material?
Standard concentration is typically a single value (very precise) vs. QC concentration is typically a range.
What is a calibration?
It compares an instrument measurement/reading to a known concentration (standard)
When is calibration ran?
Ran prior to quality control to assign a known value to an instrument output.
