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Questions and Answers
Which of the following pre-analytical variables can significantly impact lab test results?
What is meant by 'sensitivity' in laboratory testing?
Which of the following best describes precision in laboratory testing?
Why is it important to know the sample stability of different sample types?
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Which QC term indicates how close a test result is to the true value?
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What could low specificity in a test result potentially lead to?
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Which of the following factors is crucial for ensuring sample quality during venipuncture?
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What does standard deviation (SD) indicate in the context of basic QC statistics?
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Study Notes
Pre-Analytical Variables
- Pre-analytical variables impact lab test outcomes before analysis, contributing to up to 75% of lab errors.
- Patient Identification: Correct patient identification is essential for reliable results.
- Patient Preparation: Factors like fasting or diurnal variations (e.g., cortisol levels) can significantly affect test outcomes.
- Site Selection and Preparation: Proper venipuncture site selection and preparation minimizes contamination risk.
- Tourniquet Application and Venipuncture Technique: Appropriate tourniquet application time is crucial for avoiding hemolysis and ensuring sample quality.
- Special Handling: Certain samples require specialized treatment (e.g., chilled transport for ammonia or lactic acid) to maintain stability and accuracy.
- Sample Stability: Understanding the stability of whole blood, serum, and plasma at different temperatures prevents degradation and ensures accurate measurement.
Key QC Terms in Laboratory Performance
- Accuracy: Measures how closely a test result aligns with the true value. Accuracy is validated using assayed control samples with known values. Higher accuracy indicates results closer to the target value.
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Precision: Measures the consistency and reproducibility of test results for the same sample.
- Intra-assay precision: Consistency within a single test run.
- Inter-assay precision: Consistency across multiple test runs.
- High precision reduces variability, leading to improved reliability.
- Specificity: Measures if a test exclusively identifies the intended analyte. Low specificity can result in false elevations due to interference (e.g., similar hormones like FSH, LH). Poor specificity decreases the accuracy of the test.
- Sensitivity: Indicates the test's ability to detect small amounts of the analyte. Low sensitivity can compromise the test's ability to accurately measure low concentrations.
Basic QC Statistics
- Mean (Average): Represents the average value of data points; often used to establish the "true value" in a sample set.
- Standard Deviation (SD): Reflects the spread of data points from the mean; a key indicator of precision.
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Description
Explore the critical pre-analytical variables that influence lab test outcomes. Understand the impact of patient identification, preparation, site selection, and sample handling on laboratory errors. This quiz will help reinforce your knowledge on ensuring accurate and reliable test results.
