Lab

Monospot

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Monospot, Mononucleosis Spot Test, Infectious Mononucleosis Slide Test, Heterophil Antibody Test, Heterophile Antibody Test, Heterophil Agglutination Tube Test, Paul-Bunnell Test, Mononucleosis Heterophile Test, Heterophile Antibodies

  • Mechanism
  1. Test for heterophile Antibody (Paul-Bunnell IgM)
    1. Not specific to EBV
    2. Uncommonly occurs in other conditions
  2. Heterophil Antibody agglutinates Red Blood Cells
    1. Horse RBCs (most sensitive) - used for slide test
    2. Bovine RBCs
    3. Sheep RBCs (least sensitive)
  1. False negative Monospot common early in course
    1. Week 1: 25% False Negative Rate
    2. Week 2: 5-10% False Negative Rate
    3. Week 3: 5% False Negative Rate
  2. Positive Heterophile Antibody Tests
    1. Monospot positive at week 1 in 25% of patients
      1. Heterophile Antibodies are typically formed by 1 week of symptom onset
      2. But typically titers are too low for detection at this time
    2. Monospot positive by week 3 in >90% of patients
    3. Antibodies peak between weeks 2 and 5
  3. Heterophile Antibodies usually persist for 3 months
    1. Rarely antibodies persist up to 1 year
  4. Heterophile Antibody development is age specific
    1. Age under 2 years: <30% develop antibodies
    2. Age 2-4 years: <75% develop antibodies
    3. Age <12 years: <50% develop antibodies
    4. Age >12 years: >70% develop antibodies
    5. Adults >85% develop antibodies
  • References
  1. Gantz in Noble (2001) Primary Care, Mosby, p. 268
  2. Ravel (1995) Lab Medicine, Mosby-Year, p. 263-4