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Questions and Answers
What does diagnostic sensitivity measure?
What does diagnostic sensitivity measure?
- The ability to detect individuals without the disease
- The accuracy of differentiating all cases
- The ability to generate true-positive results (correct)
- The proportion of false-positive results
Why is high sensitivity important for screening tests?
Why is high sensitivity important for screening tests?
- To ensure that no case is missed (correct)
- To reduce the number of false positives
- To confirm the diagnosis of the disease
- To provide a higher accuracy rate
What does diagnostic specificity indicate?
What does diagnostic specificity indicate?
- The total number of tests conducted
- The ability to detect true-negative results (correct)
- The proportion of individuals with the disease
- The effectiveness of confirming a diagnosis
In diagnostic accuracy, what represents true positives (TP)?
In diagnostic accuracy, what represents true positives (TP)?
What is the formula used to calculate sensitivity?
What is the formula used to calculate sensitivity?
What does a test with 100% specificity indicate?
What does a test with 100% specificity indicate?
Which parameter indicates the number of cases incorrectly identified as patients?
Which parameter indicates the number of cases incorrectly identified as patients?
What does the accuracy of a diagnostic method depend on?
What does the accuracy of a diagnostic method depend on?
Which type of tests require high specificity?
Which type of tests require high specificity?
What does a receiver operator characteristic (ROC) curve compare?
What does a receiver operator characteristic (ROC) curve compare?
What is the primary purpose of intralab quality control?
What is the primary purpose of intralab quality control?
How are initial control limits established in quality control?
How are initial control limits established in quality control?
What indicates that an analytical result cannot be reported?
What indicates that an analytical result cannot be reported?
What is the benefit of using blind control samples in internal QC testing?
What is the benefit of using blind control samples in internal QC testing?
Which statement about systematic and random errors during quality control is true?
Which statement about systematic and random errors during quality control is true?
What is maintained by the analyst after each quality control run?
What is maintained by the analyst after each quality control run?
What do control samples analyze alongside?
What do control samples analyze alongside?
Which of the following is a key outcome of intralab quality control?
Which of the following is a key outcome of intralab quality control?
Why are control samples prepared at two levels during internal QC?
Why are control samples prepared at two levels during internal QC?
What program is used to check QC results after each run?
What program is used to check QC results after each run?
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Study Notes
Diagnostic Sensitivity
- Diagnostic sensitivity measures the test's ability to correctly identify individuals with a disease, yielding valid true-positive results while minimizing false-negative results.
- High sensitivity is crucial for screening tests to ensure no cases are missed.
- Sensitivity can be calculated as:
Sensitivity (%) = (Total number of diseased individuals with positive test result / Total number of diseased individuals tested) × 100
Diagnostic Specificity
- Diagnostic specificity indicates the test's ability to correctly identify individuals without the disease, leading to true-negative results and few false-positive outcomes.
- High specificity is essential for confirmatory tests that validate diagnoses.
- Specificity can be calculated as:
Specificity (%) = (Total number of individuals without disease with negative test result / Total number of individuals tested without disease) × 100
Diagnostic Accuracy
- Accuracy reflects the method's overall ability to distinguish between diseased and healthy individuals using the proportion of true positives (TP) and true negatives (TN).
- Accuracy incorporates both TP and TN along with false positives (FP) and false negatives (FN):
Accuracy = (TP + TN) / (TP + TN + FP + FN)
Key Terminology
- True Positive (TP): Correctly identified cases of disease.
- False Positive (FP): Incorrectly identified cases as having the disease.
- True Negative (TN): Correctly identified healthy cases.
- False Negative (FN): Incorrectly identified healthy cases.
Quality Control Objectives
- Quality control is intended to ensure:
- Stability of the testing machine.
- Quality of reagents used in testing.
- Minimization of technical (operator) errors.
Types of Quality Control
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Intralab Quality Control (Internal QC):
- Involves analyzing control samples alongside patient specimens.
- Detects performance changes from standard operations, essential for daily accuracy and precision monitoring.
- Identifies both random and systematic errors in testing.
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Internal QC employs blind control samples mixed with patient specimens, typically prepared at two levels representing various patient sample types.
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Initial control limits are determined by analyzing a pool over 20 consecutive runs, with periodic reevaluation.
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Results cannot be reported for any analyte declared as "out of control" after internal QC testing.
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A multi-rule quality control program is used for checking QC results after each test run, with hard copies maintained by the analyst.
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