[IM] Flashcards
What is infectious mononucleosis (IM)?
A self-limiting acute disease affecting the lymphoid tissues.
What virus causes infectious mononucleosis?
Epstein-Barr virus (EBV).
What is another name for infectious mononucleosis?
Pfeiffer’s disease or the kissing disease.
What age group is most commonly affected by IM?
Young adults and children.
What are the typical symptoms of IM?
Fever, malaise, sore throat, lymphadenopathy.
What type of immune cells are primarily affected in IM?
Lymphocytes.
What are Downey cells?
Enlarged atypical lymphocytes observed in a blood smear.
What is the primary serologic test used to diagnose IM?
Detection of IgM heterophile antibodies.
What type of antibodies are detected in the IM test?
Heterophile antibodies.
Who discovered the heterophile antibodies in IM patients?
Paul & Bunnell.
What reagent is used in the IM slide test?
Stabilized horse RBCs and latex particles.
What is the principle of the IM rapid slide test?
Heterophile antibodies in the patient’s serum react with horse RBCs, causing agglutination.
What type of RBCs are used in the IM test reagent?
Horse RBCs.
What specimen is required for the IM test?
Serum.
What is a positive result in the IM rapid slide test?
Visible red cell agglutination.
What are the false positive causes of the IM test?
Cytomegalovirus (CMV), Toxoplasmosis, acute HIV, malignancies, autoimmune diseases.
What is the sensitivity of the IM test after the first week?
90-95% after the first week.
What is the specificity of the IM test?
94%.
Why is the IM test no longer recommended by the CDC?
Due to false positives and false negatives.
What test improves the specificity of the IM heterophile antibody test?
Davidsohn differential absorption test.
What is the principle of the Paul-Bunnell test?
Mixing inactivated patient serum with sheep RBCs and observing agglutination.
What are the limitations of the Paul-Bunnell test?
Not specific; reacts with Forssman and serum sickness antibodies.
What test did Davidsohn develop to improve specificity?
An absorption method to remove Forssman antibodies and improve specificity.
What are the materials provided in the IM test kit?
IM reagent, positive and negative control sera, IM diluent, pipettes, test cards.
How should the IM reagent be stored?
Refrigerated but brought to room temperature before use.
Why must the IM test reagents be brought to room temperature before testing?
To ensure optimal antigen-antibody reaction.
How is the IM rapid slide test performed?
Mix patient serum with IM reagent, observe for visible agglutination.
What control samples are used in the IM slide test?
Positive and negative control sera.
How long should the slide be mixed before reading results?
Tilt slide for 30 seconds, leave undisturbed for 90 seconds.
What is the quantitative test for IM antibodies?
A method for determining antibody titer using serum dilutions.
What dilutions are used in the quantitative IM test?
1:2, 1:4, 1:8, 1:16.
How is the IM antibody titer determined?
Reciprocal of the highest dilution showing agglutination.
What is the Monospot test used for?
Rapid differential test for detecting IM heterophile antibodies.
What is the principle of the Monospot test?
Absorption of serum with antigens followed by reaction with horse RBCs.
What RBCs are used in the Monospot test?
Horse RBCs.
How is agglutination interpreted in the Monospot test?
Strong agglutination indicates IM.
What is the role of guinea pig kidney antigen in IM testing?
Absorbs Forssman antibodies but not IM antibodies.
How does the Davidsohn differential test distinguish IM from other conditions?
Differentiates IM antibodies from Forssman and serum sickness antibodies.
What does an eightfold reduction in the Paul-Bunnell titer indicate?
Presence of IM-specific antibodies.
What diseases can give false-positive results in the IM test?
CMV, Toxoplasmosis, Acute HIV, Leukemia, Burkitt’s Lymphoma, Serum sickness.
What is the role of beef erythrocytes in IM differential testing?
Absorbs IM heterophile antibodies for differentiation.
How are heterophile antibodies related to IM diagnosis?
They cross-react with EBV antigens, aiding in IM diagnosis.
What is the role of Epstein-Barr virus (EBV) serology in IM diagnosis?
Detects IgM and IgG antibodies against EBV-specific antigens.
What are alternative laboratory tests for IM besides heterophile antibody tests?
EBV-specific IgM and IgG serology, PCR.
What is the incubation period of infectious mononucleosis?
4-6 weeks.
How long do IM heterophile antibodies persist after infection?
Persist for months to a year.
What complications can arise from IM?
Splenic rupture, hepatitis, neurological complications.
How can IM be differentiated from CMV infection?
CMV lacks heterophile antibodies; requires PCR or CMV-specific IgM.
Why is it important to confirm IM diagnosis with specific EBV tests?
EBV-specific tests confirm the diagnosis and rule out other causes.
How should IM test results be reported?
Reported as positive (agglutination present) or negative (no agglutination).
