Diagnostic Sensitivity vs Specificity Quiz
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Questions and Answers

What is the primary purpose of screening tests concerning diagnostic sensitivity?

  • To ensure that no case of the disease is missed (correct)
  • To provide average results for general population testing
  • To minimize the rate of false positives
  • To confirm the presence of a disease in patients

    • Which of the following statements best describes diagnostic specificity?

  • It assesses the test's capacity to provide accurate results across various conditions.
  • It evaluates how many healthy individuals are correctly identified. (correct)
  • It focuses on the test's ability to minimize false negatives.
  • It determines the percentage of diseased individuals identified as healthy.

    • In the context of diagnostic accuracy, what does the formula TP + TN represent?

  • Overall effectiveness of the test regardless of disease status
  • False negatives and false positives combined
  • Total number of all subjects tested
  • True positives and true negatives correctly identified (correct)

    • What would a 100% sensitivity in a diagnostic test indicate?

    <p>Every patient with the disease is detected accurately</p> Signup and view all the answers

    When comparing two diagnostic assays on a ROC curve, what does it mean for a test to be closer to the upper-left-hand corner?

    <p>The test is more accurate in terms of sensitivity and specificity</p> Signup and view all the answers

    Which parameter is NOT included in the calculation for accuracy?

    <p>True negative ratio (TNR)</p> Signup and view all the answers

    What is the main objective of using high specificity in confirmatory tests?

    <p>To reduce the likelihood of making false positive diagnoses</p> Signup and view all the answers

    What does a false positive (FP) indicate in diagnostic testing?

    <p>A healthy individual is identified as having the disease</p> Signup and view all the answers

    Which of the following best defines true negative (TN) in diagnostic testing?

    <p>The accurate identification of healthy individuals</p> Signup and view all the answers

    How is the sensitivity of a diagnostic test expressed mathematically?

    <p>TP / Total number of diseased individuals tested x 100</p> Signup and view all the answers

    What is the primary purpose of intralab quality control (Internal QC)?

    <p>To detect changes in performance between current and stable operation</p> Signup and view all the answers

    Which of the following is NOT a type of quality control mentioned?

    <p>Process QC</p> Signup and view all the answers

    What happens if QC test results are declared 'out of control'?

    <p>No results for that analyte are reported</p> Signup and view all the answers

    How are initial control limits established in quality control?

    <p>Analyzing pool material in 20 consecutive runs</p> Signup and view all the answers

    Which errors can be detected by implementing internal QC?

    <p>Both random and systematic errors</p> Signup and view all the answers

    What role do blind control samples play in internal QC?

    <p>They are mixed with patient specimens to validate results</p> Signup and view all the answers

    Which of the following best describes the multi-rule quality control program?

    <p>A method used to check QC results after each analytical run</p> Signup and view all the answers

    In internal QC, what is monitored daily?

    <p>The accuracy and precision of analytical methods</p> Signup and view all the answers

    What is the consequence of not maintaining hardcopies of QC results?

    <p>It prevents the identification of analytical errors</p> Signup and view all the answers

    What is the primary focus of quality control in a clinical chemistry laboratory?

    <p>To ensure the quality and reliability of test results</p> Signup and view all the answers

    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

    • 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.

    • Internal QC employs blind control samples mixed with patient specimens, typically prepared at two levels representing various patient sample types.

    • Initial control limits are determined by analyzing a pool over 20 consecutive runs, with periodic reevaluation.

    • Results cannot be reported for any analyte declared as "out of control" after internal QC testing.

    • 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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    Description

    This quiz explores the concepts of diagnostic sensitivity and specificity in analytical methods. It covers how sensitivity relates to the ability of a test to generate true-positive results while minimizing false negatives. Ideal for those studying medical diagnostics and test evaluations.

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