WorksheetsBlood Gas Analysis Quiz
Total questions: 40
Worksheet time: 20mins
A blood gas analyzer shows repeated values tightly clustered together but consistently far from the known target value. Which interpretation best explains this finding?
Random error due to poor sample handling
High accuracy with low precision
High precision with poor accuracy indicating systematic error
Acceptable analytical performance
A clinician questions the reliability of a single blood gas result despite acceptable calibration. Which quality system specifically evaluates the reliability of that individual measurement?
Quality assurance
External proficiency testing
Quality control
Preventive maintenance
During routine QC review, a sudden shift of all control values above +2 SD is observed. Which error type is most likely present?
Random error
Preanalytical error
Systematic error
Clerical error
An analyzer repeatedly fails QC due to drift caused by deteriorated electrode response. This failure best reflects a problem in which QA component?
Record keeping
Preventive maintenance and function checks
Performance validation
External quality control
A QC result shows a single isolated out-of-range data point, with all previous and subsequent values within limits. What is the most likely explanation?
Bias
Systematic calibration failure
Random error
Inadequate documentation
Which action is MOST appropriate when random error is suspected during internal quality control testing?
Immediately replace the analyzer
Rerun the control with careful handling and injection technique
Ignore the result and proceed with patient testing
Report the error to the proficiency testing agency
A laboratory introduces a new blood gas analyzer. Which process confirms both accuracy and precision before clinical use?
Quality assurance review
Preventive maintenance
Performance validation
Automated calibration
Which practice BEST differentiates quality assurance from quality control?
QA focuses on individual test accuracy
QC monitors personnel competence
QA monitors all factors affecting testing and reporting
QC replaces documentation requirements
A technologist compares the measured arterial PO₂ to the calculated PAO₂ to evaluate result validity. This is an example of which QC check?
Technologic
Delta
Physiologic
External
A patient’s current base excess value is markedly different from the previous result without clinical explanation. Which QC practice would detect this discrepancy?
Physiologic check
Technologic check
Delta check
Proficiency testing
Which situation BEST represents a technologic check in blood gas quality control?
Comparing PO₂ to PAO₂
Comparing PO₂ to HbO₂ from a co-oximeter
Comparing current and previous base excess
Comparing peer laboratory results
Control media analysis consistently exceeds ±2 SD limits over several runs. What is the MOST appropriate response?
Continue patient testing if results are clinically reasonable
Investigate, correct, and document corrective actions
Repeat QC at the next shift
Ignore until external QC confirms failure
Which condition MOST commonly contributes to random analytic error during blood gas measurement?
Contaminated calibration buffers
Deteriorated electrode membranes
Air bubbles in the measuring chamber
Improper analyzer maintenance
A blood gas sample drawn from an arterial catheter shows PO₂ values approaching 150 mmHg with decreased PCO₂. Which preanalytical error is MOST likely?
Venous puncture
Air contamination
Catheter line dilution
Heparin dilution
How many levels of control media should be analyzed during an 8-hour shift when patient samples are tested?
One level
Two levels
Three levels
Four levels
A laboratory rotates control levels so that three different levels are analyzed over three consecutive shifts. What is the PRIMARY purpose of this practice?
Reduce reagent cost
Detect clerical errors
Assess analyzer performance across ranges
Meet proficiency testing requirements
Which finding MOST strongly suggests an inadvertent venous puncture during arterial sampling?
Bright red blood under pressure
High PO₂ with normal PCO₂
Dark blood with low PO₂ and elevated PCO₂
Elevated pH with low base excess
In hypotensive patients, which factor increases the risk of venous puncture during arterial blood gas sampling?
Excessive anticoagulation
Difficulty palpating arterial pulsation
Improper sample storage
Excess waste withdrawal
Which preanalytical factor MOST directly affects arterial blood gas results before the sample reaches the laboratory?
Analyzer calibration
Automated QC
Air contamination of the sample
External proficiency testing
Which group bears PRIMARY responsibility for reducing preanalytical errors in blood gas analysis?
Clinicians only
Nursing staff only
The laboratory through written procedures
Equipment manufacturers
Which action BEST prevents dilution when drawing blood from an arterial catheter line?
Flushing the line immediately before sampling
Withdrawing 5–6 times the tubing volume as waste
Using venous syringes
Increasing anticoagulant volume
A laboratory fails to attain a score of 80% in a proficiency testing event. How is this performance classified?
Acceptable
Successful
Unsatisfactory
Inconclusive
Which situation defines UNSUCCESSFUL performance in external quality control?
One failed analyte
One missed submission
Two consecutive unsatisfactory events
One score below target
Which action is REQUIRED following unsatisfactory proficiency testing performance?
Ignore if patient results are normal
Document remedial action
Replace analyzer immediately
Suspend all testing permanently
Which is an acceptable performance criterion for pH in proficiency testing?
±0.02
±0.03
±0.04
±0.05
Which acceptable limit applies to PCO₂ in proficiency testing?
±2 mmHg
±3 mmHg
±4 mmHg
±5 mmHg
Which element is ESSENTIAL when implementing additional quality control practices?
Ignoring variability limits
Defining actions when limits are exceeded
Eliminating documentation
Reducing QC frequency
Which error type represents unpredictable imprecision in measurement?
Systematic error
Bias
Random error
Preanalytical error
Bias combined with imprecision results in which overall problem?
Precision
Accuracy
Total instrument error
Acceptable variance
Which documentation BEST helps identify the source of systematic error?
Patient diagnosis
Correlation of maintenance records with QC results
Control lot numbers only
Clinician notes
Which QA element forms the foundation for demonstrating laboratory quality?
Automated calibration
Record keeping
External proficiency testing
Performance validation
Which practice MOST effectively reduces preanalytical errors in arterial puncture?
Manual heparin flushing
Larger syringe volume
Preheparinized vented syringe kits
Delayed sample analysis
Which analytic error category is MORE serious and requires investigation and documentation?
Random error
Preanalytical error
Systematic error
Clerical error
When QC results return within specifications after corrective action, what is the NEXT appropriate step?
Discontinue analyzer use
Resume patient testing
Repeat proficiency testing
Replace electrodes immediately
Which component of QA is the ONLY fully automated element in blood gas analyzers?
Preventive maintenance
Performance validation
Automated calibration
Record keeping
Which QC chart visually plots analyte values over time against SD limits?
Histogram
Scatter plot
Levey-Jennings chart
Control summary table
Which axis of a Levey-Jennings chart represents time or shift progression?
Vertical axis
Central mean line
Horizontal axis
SD lines
A single QC point outside ±2 SD with no trend is generally considered:
Systematic failure
Instrument bias
Random variation
Immediate rejection of analyzer
Which practice helps identify preanalytical errors that are not visually evident?
External proficiency testing
Additional QC checks
Automated calibration
Performance validation
Which factor MOST explains the decrease in preanalytical errors reported in the study?
Increased staff experience
Improved analyzer technology
Use of vented preheparinized syringes
Reduced sample volume
