Quality Control Flashcards
What is the definition of Quality Control?
A process to periodically examine a measurement procedure to verify that it is performing according to pre-established specifications.
What are the objectives of Quality Control?
- To check the stability of the machine
- To check the quality of reagents
- To check technical errors (personnel)
What is Statistical Quality Control (QC)?
A method that includes monitoring reagent lot changes, calibrator lot changes, and sampling the measurement process.
What are the types of errors identified in Quality Control?
- Random Error
- Systematic Error
What does the Cumulative Sum chart indicate?
It gives the earliest indication of systematic errors (trend) and is sensitive to small, persistent errors.
What is the purpose of the Youden / Twin Plot?
To compare results obtained on a high and low control serum from different laboratories.
What is the Shewhart-Levey Jennings Chart used for?
To observe values of control materials over time to determine and detect errors such as inaccuracy and imprecision.
What is the 1 2s Rule in Westgard Rules?
A rule indicating that if one control measurement exceeds two standard deviations from the mean, it signals a potential error.
What is the primary cause of a trend observed in the Shewhart-Levey Jennings Chart?
Deterioration of reagents.
What does a shift mean in the context of Quality Control?
More than six consecutive values fall on one side of the mean, indicating a potential calibration or formulation issue.
Fill in the blank: Quality Control is also called _______.
[internal quality control / statistical process control]
What are the components of a quality management system?
- Organization
- Customer focus
- Facilities and safety
- Personnel
- Purchasing and inventory
- Process management
What is the significance of equipment maintenance in Quality Control?
It ensures that the equipment is stable and fit for measurement.
True or False: Quality Control charts are only used to observe accuracy.
False
What are the common causes of errors in Quality Control?
- Improper calibration of the instrument
- Change in reagent formulation
- Major instrument maintenance
- Failure in reagent dispense system
What is one of the main causes of a downward trend in Quality Control charts?
Deterioration of light source or incubation temperature.
What does the 1 3s Rule in Westgard Rules indicate?
A rule indicating that if one control measurement exceeds three standard deviations from the mean, it signals a potential error.
What is the role of corrective actions in Quality Control?
To address any identified issues and ensure stable measurement processes.
What is meant by the term ‘nonconforming event management’ in Quality Control?
The process of managing events that deviate from established quality standards.
What does ‘continual improvement’ refer to in a Quality Management system?
Ongoing efforts to enhance products, services, or processes.
What does the 2s rule indicate?
One observation exceeds 2 SD from the target value.
The 12s rule is not recommended because it has a large false alert rate.
What does the 35 rule signify?
One observation exceeds 3 SD from the target value.
What is the significance of the 22s (22.5s) rule?
Two sequential observations, or observations for two QC samples in the same run, exceed 2 SD (or 2.5 SD) from the target value in the same direction.
What does the R45 rule detect?
Range between observations for two QC samples in the same run, or for two sequential observations of the same QC sample, exceeds 4 SD.
What is indicated by the 10x or 10m rule?
Ten sequential observations for the same QC sample are on the same side of the target value (x or mean).
The 10 rule is not recommended because it has a large false alert rate.
What does the 815 (81.55) rule refer to?
Eight sequential observations for the same QC sample exceed 1 SD (or 1.5 SD) in the same direction from the target value.
What does CUSUM stand for?
Cumulative sum of SDI for a specified number of previous results.
What is the purpose of EWMA?
Exponentially weighted moving average with newer results having more influence (weight).
What type of error does the 2s rule help detect?
Not recommended except for ‘low sigma’ measurement procedures.
Which rule detects imprecision or bias?
35 rule.
What does the 22s rule help identify?
Bias.
What does the R45 rule help identify?
Imprecision.
True or False: The 10 rule is recommended for quality control.
False.
What trends does the 815 (81.55) rule help detect?
Bias trend.
What is the primary detection purpose of CUSUM?
Bias trend.
What does the term ‘SD’ stand for?
Standard deviation.
Fill in the blank: EWMA stands for _______.
Exponentially weighted moving average.
What does SDI represent?
Standard deviation interval.
What are outliers?
Control values that are far from the main set of values
Outliers can be caused by random or systematic errors.
What do Westgard Rules pertain to?
A combination of decision criteria or control rules to determine if an analytical run is in-control or out-of-control
This system is designed to maintain quality control in laboratory settings.
What does a 12s Rule Violation indicate?
A rejection or warning rule when one control result exceeds the mean +/-2SD
This is used for screening purposes.
What action should be taken when a 135 Rule Violation occurs?
Reject the run for probable RANDOM ERROR
This occurs if 1 control observation exceeds x +/-3s.
What is the consequence of a 22s Rule Violation?
Reject the run for probable SYSTEMATIC ERROR
This happens if 2 consecutive control values are greater than x + 2s or x - 2s.
What does a 415 Rule Violation signify?
Reject the run for probable SYSTEMATIC ERROR
This occurs if 4 consecutive control values exceed the same x + 1s or x - 1s limit.
What should be done in case of an R4s Rule Violation?
Reject the run for probable RANDOM ERROR
This is triggered if the difference between 2 controls is equal to or greater than 4s.
What is the action taken for a 135 Rule Violation?
Reject the run for probable RANDOM ERROR
This is similar to the previous 135 Rule, emphasizing the need for consistency in quality control.
List the Westgard Rules in summary.
- 12s: Warning; RANDOM
- 135: Reject; RANDOM
- 22s: Reject; SYSTEMATIC
- 415: Reject; SYSTEMATIC
- R4s: Reject; RANDOM
Each rule serves a specific purpose in identifying control failures.
What is the difference between systematic error and random error?
Systematic error influences observations consistently in one direction, while random error is present in all measurements and is due to chance.
Systematic errors can be detected as positive or negative bias, whereas random errors verify differences between repeated measurements.
What are examples of random errors?
- Instrument errors
- Operator conditions
- Environmental factors
- Pipeting errors
- Mislabelling of samples
- Temperature and voltage fluctuations
- Improper mixing of samples and reagents
- Dirty optics
Random errors can arise from various unpredictable factors affecting measurements.
What characterizes a systematic error?
A systematic error consistently influences observations in one direction.
It can be detected through a positive or negative bias.
List some sources of systematic errors.
- Calibration problems
- Deterioration of reagents and controls
- Unstable and inadequate reagent blanks
- Contaminated solutions
- Failing instrumentation
- Poorly written procedures
- Incorrect sample and reagent volume
Systematic errors often stem from consistent issues in the measurement process.
Fill in the blank: Random error is present in all measurement; due to _______.
[chance]
True or False: Random errors can be attributed to specific, consistent factors.
False
Random errors are due to chance and do not stem from consistent factors.
What is a common effect of systematic errors on measurements?
They create a bias in the results.
This bias can be either positive or negative.
Fill in the blank: Systematic error can arise from _______ problems.
[calibration]
