II. Technique: Obtaining Samples

  1. Dacron Polyester swab of posterior nasopharynx
    1. Insert into posterior nostril
    2. Leave swab in place for 10 seconds
    3. Do not swab anterior nare or throat (low efficacy)
  2. Nasopharyngeal aspirate
    1. Higher efficacy than swab
    2. Requires special equipment

III. Labs: Tests Recommended by CDC (obtain both PCR and culture)

  1. Nasopharyngeal swab PCR (preferred first-line)
    1. Indicated as first-line test for Pertussis
    2. Sample obtained with nasopharyngeal Dacron or nylon swab with results back in 1-2 days
    3. Efficacy
      1. Sufficient accuracy alone (Pertussis Culture was previously recommended for confirmation)
      2. Test Sensitivity: 77 to 97%
        1. Much better Test Sensitivity than Pertussis Culture
        2. Test Sensitivity best in first 3-4 weeks (wanes after 4 weeks)
      3. Test Specificity: 88 to 97%
        1. False Negatives after 4 weeks of cough
        2. Lower Test Specificity than culture (higher False Positive Rate)
  2. Bordatella Pertussis Culture
    1. Indicated during Pertussis outbreaks and for strain identification
    2. Sample obtained with nasopharyngeal Dacron or nylon swab
      1. Requires special transport media and culture conditions
      2. Results are delayed 7-10 days
    3. Efficacy
      1. Test Specificity: 100%
      2. Test Sensitivity: 20 to 80%
        1. Low Test Sensitivity (approaches 80% only in first two weeks, then falls off towards 20%)
        2. False Negatives occur at >2 weeks from cough onset
        3. False Negatives also occur in those Pertussis vaccinated or on antibiotics
          1. After Erythromycin for 4 days: Test Sensitivity approaches 0%
  3. Pertussis Serology
    1. Indicated in late presentation from onset of cough (4-12 weeks)
    2. However, results are not standardized - Exercise caution
    3. Efficacy
      1. Test Sensitivity: 65%
      2. Test Specificity: 92%
        1. False Positives in recently vaccinated patients (within last year)
        2. False Positives in infants age <6 months (maternal antibodies)

IV. Labs: Tests Not recommended by CDC

  1. Direct fluorescent Antibody assays
    1. Low Test Sensitivity and Test Specificity

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