Medical Technologist Test Immunology and Serology 3

Question 1

Which antibody test is the gold standard for confirming Epstein-Barr virus (EBV) as the cause of infectious mononucleosis?

Accepted Answer

EBV-specific antibodies (VCA IgM/IgG, EBNA)

Answer

Monospot heterophile antibody test

Answer

Complete blood count with atypical lymphocytes

Answer

Throat culture for Group A Streptococcus

Question 2

In flow cytometry, T-helper cells are distinguished from cytotoxic T cells primarily by:

Accepted Answer

Specific surface marker (CD4 vs. CD8) expression

Answer

Cell size differences only

Answer

Forward scatter vs. side scatter patterns

Answer

Intracellular cytokine production alone

Question 3

A speckled ANA pattern with high-titer anti-U1 RNP antibodies is the hallmark of which autoimmune disease?

Accepted Answer

Mixed connective tissue disease (MCTD)

Answer

Systemic lupus erythematosus (SLE)

Answer

Rheumatoid arthritis

Answer

Sjögren syndrome

Question 4

The direct antiglobulin test (DAT) is used to detect:

Accepted Answer

IgG or complement coating patient RBCs in vivo

Answer

Free unbound antibody in patient serum

Answer

Antigen expression on reagent red cells

Answer

Cross-reactive alloantibodies from transfusion

Question 5

Which tumor marker is most significantly elevated in hepatocellular carcinoma?

Accepted Answer

AFP (alpha-fetoprotein)

Answer

PSA (prostate-specific antigen)

Answer

CEA (carcinoembryonic antigen)

Answer

CA 125

Question 6

In a competitive immunoassay, what is the relationship between patient analyte concentration and measured signal?

Accepted Answer

Inverse: higher analyte produces lower signal

Answer

Direct: higher analyte produces higher signal

Answer

No relationship; signal is fixed by antibody amount

Answer

Exponential: signal doubles with each unit of analyte

Question 7

During the hepatitis B 'window period,' which serological marker is the ONLY one detectable?

Accepted Answer

Anti-HBc IgM

Answer

Anti-HBs

Answer

HBeAg

Answer

HBsAg