This article is part 32 of our ASCP MLS Exam Practice Questions series, focusing on Immunology – Serological Infectious Disease. It provides practice material designed for medical laboratory science students and professionals preparing for the ASCP MLS certification exam. In this section, you will find 100 carefully selected MCQs (2721–2820) covering key serological tests, diagnostic principles, antigen-antibody reactions, and laboratory applications related to infectious diseases.
100 MCQs (2721-2820):
ASCP MLS Exam Practice – Part 32: Immunology (Serological Infectious Disease). Includes 100 MCQs (2721–2820) to strengthen exam preparation.
- Which serological marker of HBV infection indicates recovery and immunity?
a) Viral DNA polymerase
b) HBe antigen
c) anti-HBs
d) HBsAg - The presence of HBsAg, anti-HBc, and often HBeAg is characteristic of:
a) Early acute phase HBV hepatitis
b) Early convalescent phase HBV hepatitis
c) Recovery phase of acute HBV hepatitis
d) Past HBV infection - Which of the following is the best indicator of an acute infection with hepatitis A virus?
a) Presence of IgG antibodies to hepatitis A virus
b) Presence of IgM antibodies to hepatitis A virus
c) Sharp decline in IgG antibodies to hepatitis A virus
d) Rise in both IgM and IgG antibodies to hepatitis A virus - Which test is routinely used for detection of hepatitis B surface antigen (HBsAg) due to its high sensitivity?
a) Hemagglutination
b) Counterimmunoelectrophoresis
c) Radial immunodiffusion
d) ELISA - Chronic carriers of HBV:
a) Have chronic symptoms of hepatitis
b) Continue to carry HBV
c) Do not transmit infection
d) Carry HBV but are not infectious - Hepatitis C differs from hepatitis A because it:
a) Has a highly stable incubation period
b) Is associated with a high incidence of icteric hepatitis
c) Is associated with a high incidence of the chronic carrier state
d) Is seldom implicated in cases of posttransfusion hepatitis - Which laboratory technique is most frequently used to diagnose and follow the course of therapy of a patient with secondary syphilis?
a) Flocculation
b) Precipitation
c) Complement fixation
d) Indirect immunofluorescence - Flocculation tests for syphilis detect the presence of:
a) Reagin antibody
b) Antigen
c) Hemolysin
d) Forssman antigen - The serological test for syphilis recommended for detecting antibody in cerebrospinal fluid is:
a) Non-treponemal antibody
b) CSF-VDRL
c) FTA-ABS
d) MHA-TP - Biological false-positive VDRL reactions are frequently encountered in patients with:
a) Lupus erythematosus
b) Acquired immune deficiency syndrome (AIDS)
c) Gonorrhea
d) Tertiary syphilis - In the FTA-ABS test, a beaded pattern of fluorescence along the treponeme indicates:
a) Positive identification of Treponema pallidum
b) Presumptive diagnosis of active syphilis
c) Presence of non-treponemal antibody (NTA)
d) False-positive reaction - For diagnosis of late latent or tertiary syphilis, the most appropriate assay is:
a) RPR
b) VDRL
c) FTA-ABS
d) FTA-ABS IgM - Which of the following is characteristic of the first stage of infection with Borrelia burgdorferi?
a) Generalized rash develops within 4–6 hours of a tick bite
b) Patient may be asymptomatic except for the rash
c) Rash persists for 7–10 days
d) Serologic testing is often positive within 1 week - Which of the following is characteristic of the late stage of Lyme disease?
a) Spread to brain and spinal cord via cerebrospinal fluid
b) Development in patients refractory to antibiotic therapy
c) Arthritis, peripheral neuropathy, or encephalomyelitis
d) Resistance to antibiotic therapy - CDC recommends which method for confirmation of Lyme disease after an equivocal ELISA?
a) Southern blot
b) Western blot
c) Northern blot
d) Eastern blot - The Mantoux test for Mycobacterium tuberculosis is based on a:
a) Type III hypersensitivity reaction
b) Type II hypersensitivity reaction
c) Type I hypersensitivity reaction
d) Type IV hypersensitivity reaction - The QuantiFERON-TB Gold test measures the release of interferon gamma (IFNγ) by:
a) T cells
b) Macrophages
c) Neutrophils
d) B cells - Which cytokine is classically associated with Th1 cells?
a) Interleukin-4
b) Interferon gamma
c) Interleukin-5
d) Interferon alpha - The initial immune response following fetal infection with rubella is the production of which class of antibodies?
a) IgG
b) IgA
c) IgM
d) Both IgG and IgA - Which of the following is a live attenuated vaccine?
a) Rabies
b) Tetanus
c) Hepatitis B
d) Measles - Which assay would confirm immune status to hepatitis B virus?
a) HBsAg
b) anti-HBs
c) IgM anti-HBc
d) Hepatitis C Ag - The disappearance of HBsAg and HBeAg, persistence of anti-HBc, and appearance of anti-HBs and anti-HBe indicate:
a) Early acute HBV hepatitis
b) Early convalescent phase HBV hepatitis
c) Recovery phase of acute HBV hepatitis
d) Carrier state of acute HBV hepatitis - The 20 nm spheres and filamentous structures of HBV are:
a) Infectious
b) Circulating aggregates of HBeAg
c) Circulating aggregates of HBsAg
d) Highly infectious when present in great abundance - The antigen marker most closely associated with transmissibility of HBV infection is:
a) HBsAg
b) HBeAg
c) HBeAg
d) HBV - Which of the following is consistent with chronic active hepatitis B?
a) HBsAg (+), IgM anti-HBc (–), anti-HBc (+), anti-HBs (–)
b) HBsAg (+), IgM anti-HBc (+), anti-HBc (–), anti-HBs (–)
c) HBsAg (–), IgM anti-HBc (–), anti-HBc (+), anti-HBs (–)
d) HBsAg (–), IgM anti-HBc (–), anti-HBc (–), anti-HBs (+) - Which of the following is used to detect Legionella pneumophila in a direct immunofluorescence assay?
a) Primary antigen with fluorescent conjugate
b) Primary antibody with fluorescent conjugate
c) Secondary antigen with fluorescent conjugate
d) Secondary antibody with fluorescent conjugate - A heterophile antigen is best described as:
a) An auto-antigen
b) Existing in an unrelated animal
c) Resulting from an anamnestic response
d) An adjuvant to increase immune response - The most commonly used serological indicator of recent streptococcal infection is antibody to:
a) Streptolysin O
b) Hyaluronidase
c) NADase
d) DNA - Which of the following is true regarding mumps infection confirmation?
a) Detection of IgM within 3–4 days of symptoms; IgG within 7–10 days; 4-fold IgG rise in convalescence
b) Detection of IgM within 5 days and rash; IgG within 10–14 days apart
c) Detection of IgM with acute infection; 4-fold IgG rise between acute and convalescent sera
d) Detection of IgG at >6 months of age demonstrating post-birth infection - PCR testing for Borrelia burgdorferi:
a) Detects specific Borrelia antibodies
b) Has no cross-reactivity issues
c) Is recommended for routine positive screening tests
d) Can utilize either a fluorescent or enzyme marker - The presence of HBsAg, anti-HBc, and often HBeAg is characteristic of:
a) Early acute phase HBV hepatitis
b) Early convalescent phase HBV hepatitis
c) Recovery phase of acute HBV hepatitis
d) Past HBV infection - Which serological marker of HBV infection indicates recovery and immunity?
a) Viral DNA polymerase
b) HBe antigen
c) anti-HBs
d) HBsAg - The disappearance of HBsAg and HBeAg, the persistence of anti-HBc, the appearance of anti-HBs, and often of anti-HBe indicate:
a) Early acute HBV hepatitis
b) Early convalescent phase HBV hepatitis
c) Recovery phase of acute HBV hepatitis
d) Carrier state of acute HBV hepatitis - An example of a live attenuated vaccine used for human immunization is:
a) Rabies
b) Tetanus
c) Hepatitis B
d) Measles - What assay would confirm the immune status to hepatitis B virus?
a) HBsAg
b) anti-HBs
c) IgM anti-HBc
d) Hepatitis C Ag - The following procedure has been routinely used for detection of hepatitis B surface antigen (HBsAg) because of its high level of sensitivity:
a) Hemagglutination
b) Counterimmunoelectrophoresis
c) Radial immunodiffusion
d) ELISA - Which of the following is the best indicator of an acute infection with the hepatitis A virus?
a) The presence of IgG antibodies to hepatitis A virus
b) The presence of IgM antibodies to hepatitis A virus
c) A sharp decline in the level of IgG antibodies to hepatitis A virus
d) A rise in both IgM and IgG levels of antibody to hepatitis A virus - The classic antibody response pattern following infection with hepatitis A is:
a) Increase in IgM antibody—decrease in IgM antibody—increase in IgG antibody
b) Detectable presence of IgG antibody only
c) Detectable presence of IgM antibody only
d) Decrease in IgM antibody—increase in IgG antibody of the IgG3 subtype - The primary marker of hepatitis B virus infection is:
a) anti-HBs
b) HBsAg
c) anti-HBc
d) HBeAg - Which antibody persists for life and indicates past infection with HBV?
a) IgM anti-HBc
b) IgG anti-HBc
c) HBeAg
d) HBsAg - Which hepatitis virus is DNA-based?
a) HAV
b) HBV
c) HCV
d) HEV - In chronic hepatitis B infection, the following marker remains positive:
a) HBsAg
b) anti-HBs
c) IgM anti-HBc
d) anti-HAV IgM - A “window period” in HBV infection is characterized by:
a) HBsAg positive, anti-HBs positive
b) Both HBsAg and anti-HBs negative
c) anti-HBs positive only
d) HBeAg positive only - Which antibody appears first in HBV infection?
a) anti-HBs
b) IgM anti-HBc
c) IgG anti-HBc
d) anti-HBe - A patient with positive HBsAg for more than 6 months is classified as:
a) Acute hepatitis B
b) Chronic hepatitis B
c) Recovery from hepatitis B
d) Immunized - Which hepatitis virus is most commonly transmitted via the fecal-oral route?
a) HBV
b) HCV
c) HAV
d) HDV - A healthcare worker vaccinated for HBV should be tested for:
a) anti-HBc IgM
b) anti-HBs
c) HBsAg
d) HBeAg - Hepatitis D virus requires the presence of:
a) HCV
b) HAV
c) HBV
d) HEV - Which marker indicates active viral replication in HBV?
a) anti-HBc IgG
b) HBeAg
c) anti-HBe
d) anti-HBs - In hepatitis C, the most reliable marker for ongoing infection is:
a) anti-HCV IgM
b) HCV RNA
c) HCV core antigen
d) anti-HCV IgG - Hepatitis E virus resembles:
a) HBV
b) HAV
c) HCV
d) HDV - Which hepatitis virus is associated with high mortality in pregnant women?
a) HAV
b) HBV
c) HCV
d) HEV - The incubation period of hepatitis A virus is approximately:
a) 15–45 days
b) 30–180 days
c) 2–4 days
d) 7–10 days - The incubation period of hepatitis B virus is approximately:
a) 7–10 days
b) 15–45 days
c) 30–180 days
d) 1–2 days - The incubation period of hepatitis C virus is approximately:
a) 2–4 days
b) 15–45 days
c) 2–26 weeks
d) 1–2 years - The incubation period of hepatitis E virus is approximately:
a) 2–9 weeks
b) 2–4 days
c) 30–180 days
d) 15–20 hours - Fulminant hepatitis is most commonly associated with:
a) HAV
b) HEV
c) HCV
d) HDV + HBV co-infection - Which hepatitis virus has the highest risk of progressing to chronic infection?
a) HAV
b) HBV
c) HCV
d) HEV - Which hepatitis virus does not have a chronic carrier state?
a) HAV
b) HBV
c) HCV
d) HDV - Which test differentiates between acute and chronic HBV?
a) anti-HBs
b) IgM anti-HBc
c) IgG anti-HBc
d) HBeAg - Vertical transmission is most common with:
a) HAV
b) HBV
c) HCV
d) HEV - Which hepatitis virus is an RNA virus from the Flavivirus family?
a) HAV
b) HBV
c) HCV
d) HEV - Which hepatitis virus can only replicate in the presence of HBV?
a) HAV
b) HCV
c) HDV
d) HEV - The surface antigen of HBV is used for:
a) Diagnostic screening
b) Immunization
c) Carrier detection
d) All of the above - Which hepatitis virus is most likely to cause hepatocellular carcinoma?
a) HAV
b) HBV
c) HCV
d) HEV - The vaccine for hepatitis B is prepared from:
a) Killed virus
b) Live attenuated virus
c) Recombinant HBsAg
d) Whole viral particles - Which hepatitis virus has no vaccine available?
a) HAV
b) HBV
c) HCV
d) HEV - Anti-HBs positivity alone indicates:
a) Past infection
b) Immunity due to vaccination
c) Chronic carrier state
d) Early acute infection - Which hepatitis virus is most resistant to heat and detergents?
a) HAV
b) HBV
c) HCV
d) HEV - HBsAg in serum for more than 6 months defines:
a) Acute HBV
b) Chronic HBV
c) Immunity
d) Recovery - Which of the following is a defective RNA virus?
a) HAV
b) HCV
c) HDV
d) HEV - Which hepatitis virus is classified under Picornaviridae?
a) HAV
b) HBV
c) HCV
d) HEV - The most common cause of post-transfusion hepatitis is:
a) HAV
b) HBV
c) HCV
d) HEV - Superinfection with HDV in an HBV carrier often leads to:
a) Recovery
b) Fulminant hepatitis
c) Immunity
d) Mild infection - The “Australia antigen” is another name for:
a) HBeAg
b) HBsAg
c) anti-HBc
d) anti-HBs - Which hepatitis virus is most likely to cause chronic cirrhosis?
a) HAV
b) HBV
c) HCV
d) HEV - Which test indicates protective immunity after HBV vaccination?
a) anti-HBc IgM
b) HBsAg
c) anti-HBs
d) HBeAg - Which hepatitis virus is associated with zoonotic transmission (pigs, boars)?
a) HAV
b) HBV
c) HCV
d) HEV - What type of sample is most commonly used in serological tests for detection of antibodies?
a) Plasma
b) Whole blood
c) Serum
d) Urine - Which immunoglobulin class is most effective at agglutination of particulate antigens in primary immune response?
a) IgG
b) IgM
c) IgA
d) IgE - In a precipitation reaction, which of the following must be true?
a) Antigen must be insoluble
b) Antibody must be insoluble
c) Both antigen and antibody are soluble
d) Neither antigen nor antibody are soluble - What is the “prozone phenomenon” in serology?
a) Antigen excess leading to false negatives
b) Antibody excess leading to false negatives
c) Perfect equivalence of antigen and antibody
d) Complete precipitation of antigen-antibody complexes - Which test is used to detect antinuclear antibodies (ANA) in autoimmune infections that may complicate infectious disease diagnosis?
a) ELISA
b) Indirect immunofluorescence
c) Agglutination
d) Western blot - Which complement component is common to both the classic and alternative complement activation pathways?
a) C1q
b) C2
c) C3
d) C5 - In a competitive ELISA for antigen detection, what happens as the concentration of patient antigen increases?
a) Signal increases
b) Signal decreases
c) No change in signal
d) Only background signal appears - The RPR test for syphilis detects:
a) Direct treponemal antigens
b) Specific anti-Treponema antibodies
c) Nontreponemal antibodies (reagins)
d) Treponema pallidum DNA - What does a four-fold rise in titer of antibody between acute and convalescent sera usually indicate?
a) Vaccine response
b) Chronic infection
c) Recent or ongoing infection
d) Prior immunity - Which of the following is a live attenuated vaccine?
a) Hepatitis B recombinant vaccine
b) Rabies inactivated vaccine
c) Yellow fever vaccine
d) Tetanus toxoid - Which serologic marker is used to determine if an HIV infection is recent or long-standing?
a) p24 antigen
b) HIV RNA load
c) IgG avidity assay
d) Total anti-HIV antibody titer - What is the major advantage of chemiluminescent immunoassays (CLIA) over standard ELISA?
a) Lower cost
b) Faster turnaround time and higher sensitivity
c) Simpler technique
d) Less reagent use - In passive immunization, what is given to the patient?
a) Live attenuated pathogen
b) Killed pathogen
c) Preformed antibodies
d) Antigen components - Which of the following serological tests is most specific for diagnosing Lyme disease after initial screening?
a) ELISA
b) RPR
c) Western blot
d) IFA (indirect fluorescent assay) - Which is the principle behind hemagglutination inhibition tests?
a) Antibodies prevent agglutination of red blood cells by antigen
b) Antigens coated on RBCs get neutralized by antibodies
c) RBCs inhibit antigen-antibody binding in solution
d) Complement mediated RBC lysis - Which marker would be positive first after infection with Epstein-Barr Virus (EBV)?
a) VCA-IgG
b) VCA-IgM
c) EBNA (EBV nuclear antigen)
d) EA (early antigen) - Which one of these is NOT an acute phase reactant?
a) C-reactive protein (CRP)
b) Fibrinogen
c) Albumin
d) Haptoglobin - For diagnosis of congenital infections (e.g., congenital syphilis), which method is most reliable?
a) Maternal serology only
b) Neonatal IgG serology
c) Neonatal IgM detection or PCR of pathogen
d) Clinical signs in the neonate - Which immunoglobulin class is most abundant on mucosal surfaces and in secretions?
a) IgG
b) IgM
c) IgA
d) IgE - In serological tests, what effect does rheumatoid factor (RF) sometimes have on results?
a) Enhances specificity
b) Causes false negatives in ELISA
c) Causes false positives by binding IgG
d) No effect at all - What is the role of neutralization assays in serology?
a) To measure antigen concentration
b) To quantify total antibody levels
c) To assess functional antibody that can block infection
d) To detect autoantibodies - Which of the following is characteristic of secondary immune responses compared to primary?
a) IgM appears first and in higher concentration
b) Slower response time
c) IgG appears rapidly and in higher concentration
d) Only IgA produced
📌 How to Use This Practice Set
- Answer each question before checking the key.
- Focus on why the correct answer is right and the others are wrong.
- Use this set as timed practice to simulate the real exam environment.
Answer Key
Answer Key:
- c) anti-HBs
- a) Early acute phase HBV hepatitis
- b) Presence of IgM antibodies to hepatitis A virus
- d) ELISA
- b) Continue to carry HBV
- c) Is associated with a high incidence of the chronic carrier state
- d) Indirect immunofluorescence
- a) Reagin antibody
- b) CSF-VDRL
- a) Lupus erythematosus
- d) False-positive reaction
- c) FTA-ABS
- b) Patient may be asymptomatic except for the rash
- c) Arthritis, peripheral neuropathy, or encephalomyelitis
- b) Western blot
- d) Type IV hypersensitivity reaction
- a) T cells
- b) Interferon gamma
- c) IgM
- d) Measles
- b) anti-HBs
- c) Recovery phase of acute HBV hepatitis
- c) Circulating aggregates of HBsAg
- b) HBeAg
- a) HBsAg (+), IgM anti-HBc (–), anti-HBc (+), anti-HBs (–)
- b) Primary antibody with fluorescent conjugate
- b) Existing in an unrelated animal
- a) Streptolysin O
- c) Detection of IgM with acute infection; 4-fold IgG rise between acute and convalescent sera
- (((d) Can utilize either a fluorescent or enzyme marker))
- a) Early acute phase HBV hepatitis
- c) anti-HBs
- c) Recovery phase of acute HBV hepatitis
- d) Measles
- b) anti-HBs
- d) ELISA
- b) The presence of IgM antibodies to hepatitis A virus
- a) Increase in IgM antibody—decrease in IgM antibody—increase in IgG antibody
- b) HBsAg
- b) IgG anti-HBc
- b) HBV
- a) HBsAg
- b) Both HBsAg and anti-HBs negative
- b) IgM anti-HBc
- b) Chronic hepatitis B
- c) HAV
- b) anti-HBs
- c) HBV
- b) HBeAg
- b) HCV RNA
- b) HAV
- d) HEV
- a) 15–45 days
- c) 30–180 days
- c) 2–26 weeks
- a) 2–9 weeks
- d) HDV + HBV co-infection
- c) HCV
- a) HAV
- b) IgM anti-HBc
- b) HBV
- c) HCV
- c) HDV
- d) All of the above
- b) HBV
- c) Recombinant HBsAg
- c) HCV
- b) Immunity due to vaccination
- a) HAV
- b) Chronic HBV
- c) HDV
- a) HAV
- c) HCV
- b) Fulminant hepatitis
- b) HBsAg
- c) HCV
- c) anti-HBs
- d) HEV
- c) Serum
- b) IgM
- c) Both antigen and antibody are soluble
- b) Antibody excess leading to false negatives
- b) Indirect immunofluorescence
- c) C3
- b) Signal decreases
- c) Nontreponemal antibodies (reagins)
- c) Recent or ongoing infection
- c) Yellow fever vaccine
- c) IgG avidity assay
- b) Faster turnaround time and higher sensitivity
- c) Preformed antibodies
- c) Western blot
- a) Antibodies prevent agglutination of red blood cells by antigen
- b) VCA-IgM
- c) Albumin
- c) Neonatal IgM detection or PCR of pathogen
- c) IgA
- c) Causes false positives by binding IgG
- c) To assess functional antibody that can block infection
- c) IgG appears rapidly and in higher concentration
Top 8 Medical Laboratory Scientist (MLS) Exams:
Top 8 Medical Laboratory Scientist (MLS) Exams that are recognized globally and can help professionals validate their credentials and enhance their career opportunities:
1. ASCP – American Society for Clinical Pathology (USA)
- Exam Name: MLS(ASCP)
- Eligibility: Bachelor’s degree with clinical laboratory experience.
- Global Recognition: High
- Purpose: Certifies Medical Laboratory Scientists in the United States and internationally.
2. AMT – American Medical Technologists (USA)
- Exam Name: MLT(AMT) or MT(AMT)
- Eligibility: Academic and/or work experience in medical laboratory technology.
- Global Recognition: Moderate
- Purpose: Credentialing for medical technologists and technicians.
3. AIMS – Australian Institute of Medical and Clinical Scientists
- Exam Name: AIMS Certification Exam
- Eligibility: Assessment of qualifications and work experience.
- Recognition: Required for practice in Australia.
- Purpose: Certification and registration in Australia.
4. CSMLS – Canadian Society for Medical Laboratory Science
- Exam Name: CSMLS General or Subject-specific Exams
- Eligibility: Graduation from a CSMLS-accredited program or equivalent.
- Recognition: Canada
- Purpose: Entry-to-practice certification in Canada.
5. IBMS – Institute of Biomedical Science (UK)
- Exam Name: Registration and Specialist Portfolio Assessment
- Eligibility: Accredited degree and lab experience.
- Recognition: UK and some Commonwealth countries.
- Purpose: Biomedical Scientist registration with the HCPC (UK).
6. HAAD / DOH – Department of Health, Abu Dhabi (UAE)
- Exam Name: DOH/HAAD License Exam
- Eligibility: Degree in medical laboratory science and experience.
- Recognition: UAE (Abu Dhabi)
- Purpose: Licensure for medical laboratory practice in Abu Dhabi.
7. DHA – Dubai Health Authority (UAE)
- Exam Name: DHA License Exam for Medical Laboratory Technologists
- Eligibility: Relevant degree and experience.
- Recognition: Dubai, UAE
- Purpose: Professional license for clinical laboratory practice in Dubai.
8. MOH – Ministry of Health (Gulf Countries like UAE, Saudi Arabia, Kuwait)
- Exam Name: MOH License Exam
- Eligibility: BSc/Diploma in Medical Laboratory + experience.
- Recognition: Varies by country.
- Purpose: Required for practicing in public and private sector labs.
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