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QUALITY CONTROL
| Question | Answer |
|---|---|
| Quality assurance oversees all three phases of lab testing, while Quality Control only monitors WHAT section of testing? | analytical |
| What is Internal QC? | statistical data that documents the daily precision of assay measurements |
| What is External QC? | data gathered to describe the accuracy of assay measurements |
| What is Quality Control (QC)? | A system that gathers data on the reliability of assays, equipment, and reagents to analyze them to take corrective actions that'll improve lab testing in the long-term |
| How is Internal QC conducted? | The controlled specimen is run as a genuine patient sample would be. This is done to collect data that prove overall reliability of results within the lab |
| Why are controlled specimens lyophilized or in liquid form? | - good stability - reasonable expiration dating |
| What is a controlled specimen? | a substance that resembles a patient semple with an expected range of analyte being measured |
| Why would individual agencies/vendors like CAP provide patient samples to be run for Quality Control puposes? | To ensure consensus among the labs and competency of the individual technicians |
| How many levels levels of medical decision points are made with standards in place? | 2-3 |
| What is the difference between standards and calibrators? | s: highly pure substance with a known concentration that is able to measure great accuracy an establish reference points to construct graphs or calculate a test result c: a substance/machine that adjusts an instrument to properly standardize the assay |
| An aliquot of blood is an example of a (sample/population) | sample |
| What are the functions of running control specimen? | - detect errors in equipment, reagents, or individual technique - confirm stability and accuracy of testing - find errors in testing |
| Controlled specimen, when ran, indicate the overall (blank) of test results | reliability |
| What does the coefficient of variation (CV) measure? | The reproducibility (precision) of a test |
| What is meant by a True Positive (TP)? | test was positive, and disease is present |
| What is meant by a True Negative (TN)? | test was negative, and disease was not present |
| What is meant by a False Positive (FP)? | test was positive, but no disease was present |
| What is meant by a False Negative (FN)? | test was negative, but disease was present |
| Define "Sensitivity" | the ability to detect small amounts of an analyte |
| Define "Specificity" | the ability to detect a singular analyte being tested and NOT SIMILARITIES |
| Poor specificity results in | false positives |
| How is External QC conducted? | It is organized by an independent vendor that provides patient samples to the lab (to be run like normal) and they are sent back to the vendor. This is meant to ensure census between labs and individual techs |
| Quality Control uses statistical methods like the Levey-Jennings chart to determine the (blank) | reliability of test procedures/results and instrument/technician performance |
| True or False: A control matrix is included with a patient sample when performing an assay | true |
| What is meant by "to treat or not to treat"? | Controls contain expected concentration values that are used to cover medical decision points. They are shown as concerns for physicians and other medical personnel to pay attention to |
| How do we preserve the integrity of our control matrix? | Storing it in small aliquots that would (ideally) last 1 year |
| If the control materials are frozen, lyophilized, or chemically preserved, they require very accurate | reconstitution |
| Define "Reconstitution" | the process of adding liquid to a powdered substance for uniformity |
| What are the three medical decision points found in control specimens? | normal, abnormal low, abnormal high |
| What type of control material is the most expensive, and why? | Assayed controls; the controls are tested by manufacturers |
| What type of control material is the least expensive, and why? | In-house controls; they are typically pooled sera, characterized by population, that is then aliquoted for everyday use |
| What is Qualitative Testing? | Testing that determines the presence or absence of a substance |
| What is Quantitative Testing? | Testing that measures the amount of a substance present |
| What is the main goal of establishing control ranges? | Create an acceptable range that reduces variability due to error and chance |
| What are the levels of control in the Qualitative System? | positive, negative, weak positive |
| What are the levels of control in the Quantitative System? | normal, abnormal low/high |
| What calculations are done to determine the "central tendency" of a data set? | mean, median, mode |
| What calculations are done to describe the dispersion/variability of data around the mean? | range, standard deviation, variance, coefficient of variation |
| What is a Youden plot, and what does it do? | It is a graph made up of 2 Levey-Jennings charts at right angles, and it is used to plot 2 controls |
| What is the purpose of Westgard Rules? | It uses the premise that 95.5% of control values should fall within (+ or -) 2 standard deviations to determine whether or not an analytical run is in/out of control |
| Which Westgard Rule is considered a warning sign instead of a sign of rejection? | 1 2s |
| Define the 1 2s rule | It happens when one control measurement supersedes the 2 standard deviation control limits from the mean |
| When a control of 2 out of 3 control measurements exceeds the mean by 2SD, what is this called? | 2of3 2S |
| When a run is rejected due to a singular control value being exceeding a 3SD limit, this is WHAT rule? | 1 3s |
| Define the 2 2s rule | A run is rejected when 2 consecutive control measurements that exceed the mean by 2 standard deviations on the same side |
| What kind of rule is in effect if a run is rejected due to the 4th consecutive control exceeding 1 standard deviation on the same side of the mean? | 4 1s |
| Define the "10x" Westgard Rule. | The run is rejected when 10 consecutive controls on the same run are on the same side of the mean |
| When a run has 3 consecutive control measurements exceed the same mean by 1 standard deviation, what rule must be followed? | 3 1s |
| Define 6x rule | When 6 control values from ONE control fall on the same, singular side of the mean |
| A large amount of scatter about the mean is typically the result of | imprecision (eg. individual technique) |
| A change in the testing process can result in an | inaccuracy trend/shift |
| A sudden, rapid change away from the mean that creates unidirectional bias can be referred to as a | shift |
| Define a trend/drift | a gradual change overtime in one direction (ie. 6 consecutive points) |
| What is a Delta Check? | when patient samples from an earlier period of time are compared to a current specimen. this is to determine stability and reliability |
| What is a systemic error? | a predictable change that causes shifts or trends on control charts |
| What is a random error? | Imprecision that causes a spread of control values around the mean |
| What does it mean for a control chart to have values across the mean? | The values are in all 3 levels of control |
| What does it mean for a control chart to have values within the mean? | The values are observed across multiple days |
| What is an assayed control? | a substance with a known range of analyte that mimics human blood |
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innazukaa
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