Preparing for the ASCP MLS (Medical Laboratory Scientist) exam requires a strong grasp of immunology concepts, especially serological procedures and test interpretation. These tests are critical in diagnosing infections, autoimmune disorders, allergies, and immune deficiencies.
This practice set provides 100 MCQs (Questions 2921–3020) focusing on serological test results in immunology. It is designed for medical and lab students as well as laboratory professionals who want to test their knowledge and improve exam readiness.
100 MCQs (2921-3020):
This practice exam set (2921–3020) focuses on serological test results in immunology. It covers infectious disease serology, autoimmune markers, complement activity, hypersensitivity, antigen-antibody reactions, and interpretation of test patterns.
- Which type of sample is most commonly used for serological testing?
a) Plasma
b) Whole blood
c) Serum
d) Urine - The presence of IgM antibodies in a serological test usually indicates:
a) Past infection
b) Recent or acute infection
c) Immunity after vaccination
d) Non-specific reaction - A positive direct Coombs (DAT) test indicates:
a) Free antibodies in serum
b) Antibodies bound to red blood cells in vivo
c) Complement deficiency
d) Autoimmune neutropenia - Which test is commonly used to detect syphilis?
a) VDRL
b) ELISA for HIV
c) Widal test
d) Monospot test - A fourfold rise in antibody titer between acute and convalescent sera suggests:
a) No infection
b) Acute infection
c) Past exposure only
d) False-positive result - Which immunoglobulin is most associated with secondary immune response?
a) IgM
b) IgA
c) IgG
d) IgE - A false-positive serological test can result from:
a) High antibody specificity
b) Cross-reactivity
c) Monoclonal antibodies
d) Proper washing of wells - Which serological test is used as a screening tool for HIV?
a) Western blot
b) ELISA
c) PCR
d) Immunofluorescence - The confirmatory test for HIV after a positive ELISA is:
a) Agglutination test
b) Western blot
c) Hemagglutination inhibition
d) Immunodiffusion - Which of the following is a non-treponemal test?
a) TP-PA
b) FTA-ABS
c) RPR
d) ELISA - A serological test that detects antigen-antibody precipitation in gel is:
a) ELISA
b) Immunodiffusion
c) Agglutination
d) Complement fixation - HBsAg positivity in a patient suggests:
a) Past infection
b) Current HBV infection
c) Recovery phase
d) Immunity after vaccination - The presence of anti-HBs indicates:
a) Active hepatitis B
b) Susceptibility to infection
c) Immunity (past infection or vaccination)
d) Viral replication - In the Monospot test for infectious mononucleosis, heterophile antibodies cause:
a) Agglutination of sheep RBCs
b) Precipitation in agar
c) Complement fixation
d) Fluorescent staining - A patient with anti-HCV positive and HCV RNA positive likely has:
a) Past resolved infection
b) Acute or chronic hepatitis C
c) Vaccination-induced immunity
d) No infection - Which immunoglobulin is first detected in primary response?
a) IgA
b) IgM
c) IgE
d) IgG - Complement fixation test is positive when:
a) Hemolysis occurs
b) Hemolysis is absent
c) Agglutination is seen
d) Fluorescence is present - Which test uses enzyme-labeled antibodies to detect antigen-antibody reactions?
a) ELISA
b) Immunodiffusion
c) Agglutination
d) PCR - In rheumatoid arthritis, serological tests often detect:
a) Anti-dsDNA
b) Rheumatoid factor (RF)
c) HBsAg
d) ANA - The Paul-Bunnell test is associated with:
a) Malaria
b) Infectious mononucleosis
c) Syphilis
d) Tuberculosis - ANA (antinuclear antibody) testing is mainly used in diagnosing:
a) Hepatitis B
b) HIV
c) Systemic lupus erythematosus (SLE)
d) Syphilis - A prozone effect in serological testing may lead to:
a) False negative result
b) False positive result
c) Increased sensitivity
d) No effect - In serology, a heterophile antibody is best described as:
a) An antibody reacting with unrelated antigens
b) An autoantibody against DNA
c) A complement-fixing antibody
d) A monoclonal antibody - A positive cold agglutinin test is often associated with:
a) Influenza A
b) Mycoplasma pneumoniae infection
c) HIV
d) Hepatitis B - Detection of anti-dsDNA is highly specific for:
a) SLE
b) RA
c) HIV
d) HBV - Which of the following is a treponemal test?
a) RPR
b) VDRL
c) FTA-ABS
d) Cold agglutinin - High titers of anti-streptolysin O (ASO) indicate:
a) Acute rheumatic fever or glomerulonephritis
b) Infectious mononucleosis
c) Chronic hepatitis
d) Tuberculosis - In HIV serology, the “window period” refers to:
a) Time between exposure and symptom onset
b) Time between infection and detectable antibodies
c) Time between ELISA and Western blot
d) Time between treatment and recovery - A positive heterophile antibody test with clinical symptoms suggests:
a) Syphilis
b) Infectious mononucleosis
c) Malaria
d) HBV infection - Which immunoglobulin crosses the placenta to provide passive immunity?
a) IgM
b) IgG
c) IgA
d) IgE - A rising IgG titer in convalescent serum suggests:
a) No infection
b) Current or past infection
c) Laboratory error
d) Early primary infection - Which test is commonly used for rapid diagnosis of group A streptococcal infection?
a) ELISA
b) Latex agglutination
c) Western blot
d) Immunodiffusion - In serological testing, a titer is defined as:
a) The highest dilution showing a positive reaction
b) The lowest dilution of antibody
c) Concentration of antigen
d) Total serum protein - The presence of IgE antibodies in a serological test is most associated with:
a) Viral infections
b) Parasitic infection or allergy
c) Autoimmune disease
d) Bacterial infection - A positive CRP (C-reactive protein) test indicates:
a) Autoimmunity
b) Acute inflammation
c) Viral hepatitis
d) Allergic disease - In the Widal test, a significant diagnostic finding is:
a) Single low titer
b) Fourfold rise in O or H antibodies
c) Negative reaction
d) Presence of IgE antibodies - The heterophile antibody test is primarily used in:
a) Hepatitis
b) HIV
c) Infectious mononucleosis
d) Malaria - A serological test for Helicobacter pylori detects:
a) Antigen in stool
b) Urease activity
c) Antibody in serum
d) Viral load - In complement fixation tests, hemolysis indicates:
a) Positive result
b) Negative result
c) Equivocal result
d) Cross-reaction - A false-negative in serological testing due to excess antigen is known as:
a) Hook effect
b) Cross-reaction
c) Prozone effect
d) Antigen excess - Detection of anti-HBc IgM indicates:
a) Past HBV infection
b) Current acute HBV infection
c) Immunity by vaccine
d) Carrier state only - Which technique uses fluorescence-labeled antibodies?
a) ELISA
b) Western blot
c) Immunofluorescence
d) Agglutination - The presence of both HBsAg and HBeAg suggests:
a) Chronic inactive HBV infection
b) Active viral replication
c) Complete recovery
d) Immunity by vaccination - A test useful for detecting cold agglutinins is:
a) ANA
b) Widal test
c) Donath-Landsteiner test
d) ASO titer - A positive VDRL test but negative treponemal test suggests:
a) Past syphilis
b) Biological false-positive
c) Current syphilis
d) Secondary syphilis - Serological detection of heterophile antibodies against horse RBCs is seen in:
a) Paul-Bunnell test
b) ELISA
c) Widal test
d) TP-PA - Which test detects antibodies to Borrelia burgdorferi (Lyme disease)?
a) Widal test
b) Western blot and ELISA
c) Monospot test
d) RPR test - A screening test for autoimmune thyroid disease is:
a) ANA test
b) Anti-thyroglobulin antibody test
c) RPR
d) VDRL - Serological tests detecting IgG subclasses are useful in:
a) Allergy diagnosis
b) Immune deficiency evaluation
c) Hepatitis B infection
d) HIV confirmation - Antistreptolysin O (ASO) titer helps in diagnosing:
a) Recent streptococcal infection
b) HIV
c) HBV
d) Syphilis - Which serological test identifies antibodies by separating proteins on a membrane?
a) ELISA
b) Western blot
c) Agglutination
d) Complement fixation - In rheumatoid arthritis, which antibody is commonly detected?
a) Anti-dsDNA
b) ANA
c) Rheumatoid factor
d) Anti-HBc - Which hepatitis marker indicates immunity after vaccination?
a) HBsAg
b) Anti-HBs
c) Anti-HBc IgM
d) HBeAg - The Weil-Felix test detects antibodies against:
a) Rickettsial infections
b) Hepatitis viruses
c) Treponema pallidum
d) HIV - Which serological test uses latex beads coated with antigen or antibody?
a) Immunodiffusion
b) Latex agglutination
c) ELISA
d) PCR - Serological detection of CMV infection in newborns is best done using:
a) IgG antibodies
b) IgM antibodies
c) HBsAg
d) ANA - A non-treponemal test for syphilis is:
a) TP-PA
b) FTA-ABS
c) RPR
d) Western blot - Which immunoglobulin predominates in mucosal secretions?
a) IgG
b) IgA
c) IgM
d) IgE - The rose bengal test is used in the diagnosis of:
a) Brucellosis
b) Tuberculosis
c) Malaria
d) HIV - Which test is most specific for systemic lupus erythematosus (SLE)?
a) ANA
b) Anti-dsDNA
c) RPR
d) ASO titer - A 25-year-old woman has Raynaud phenomenon, muscle pain, joint pain, and difficulty swallowing. Her ANA titer is very high (1:5120) with a speckled pattern and staining of mitotic cells. Which additional antibody is most likely present?
a) Anti-dsDNA with low complement (CH₅₀)
b) Anti-Sm antibody
c) Rheumatoid factor
d) Anti-RNP antibody - In evaluating diagnostic tests, sensitivity is the percentage of:
a) True positive cases correctly identified
b) False positive cases
c) True negative cases correctly identified
d) False negative cases - During the recovery phase of viral infection, the most useful diagnostic method is:
a) Slide culture
b) Serological antibody testing
c) Shell vial culture
d) Growth on McCoy cells - A 16-year-old with infectious mononucleosis shows a cold agglutinin titer of 1:2000. Which factor is most important in determining clinical significance?
a) Thermal amplitude (temperature range)
b) Titer measured at 4°C
c) Antibody specificity
d) Light chain class - The CH₅₀ assay is used to measure:
a) Overall complement system activity
b) Serum factor B level
c) A single complement protein
d) Only C3 concentration - A patient receiving mouse monoclonal antibody therapy shows a false-positive sandwich assay. The cause is:
a) Mouse antibody binding to antigen
b) Human anti-mouse antibody (HAMA) activity
c) Antibody against a mouse virus
d) Monoclonal gammopathy - Calculate the absolute B lymphocyte count:
WBC = 8930/μL
Lymphocytes = 30%
B lymphocytes = 40%
a) 1072/μL
b) 2679/μL
c) 3572/μL
d) 6251/μL - In flow cytometry, labeled cells:
a) Scatter light and absorb fluorescence
b) Absorb fluorescence and send electronic signals
c) Scatter light and emit fluorescence
d) Absorb both fluorescence and light - A patient’s counts are: WBC = 10,000/μL; lymphocytes = 25%; T cells = 40%. What is the absolute T cell count?
a) 200/μL
b) 1000/μL
c) 2000/μL
d) 2500/μL - WBC = 5000/μL; lymphocytes = 15%; CD4 = 8%. What is the absolute CD4 count?
a) 40/μL
b) 60/μL
c) 400/μL
d) 750/μL - Abnormal lymphocytes positive for CD2, negative for surface immunoglobulin, and lacking complement receptors suggest:
a) T cell disorder
b) B cell disorder
c) Monocyte disorder
d) NK cell disorder - A patient with suspected Lyme disease has two equivocal ELISA results. The next best test is:
a) Western blot
b) Southern blot
c) Northern blot
d) Eastern blot - Which test is NOT used for syphilis diagnosis?
a) RPR
b) TPHA
c) VDRL
d) RAST - The best method to monitor treatment response in chronic hepatitis B is:
a) HBV DNA quantification by PCR
b) Anti-HBc antibody testing
c) Anti-HBs antibody testing
d) IgM anti-HBc testing - Which finding confirms an acute mumps infection?
a) IgM detectable within a few days, with IgG rise later
b) IgM detected at 5 days plus rash
c) IgM during acute illness and IgG rise during convalescence
d) IgG after 6 months of age - A 37-year-old man with fever, nausea, fatigue, dark urine, and a tattoo history most likely has:
a) Hepatitis B
b) Hepatitis D
c) Hepatitis C
d) Hepatitis A - In a 17-year-old girl with sore throat, fever, and lymphadenopathy, which condition should be excluded?
a) Group A streptococcal infection
b) Infectious mononucleosis
c) HIV infection
d) Rotavirus infection - Which serological finding is most associated with systemic lupus erythematosus (SLE)?
a) Homogeneous ANA pattern with anti-dsDNA antibodies
b) Centromere ANA pattern with anti-centromere B
c) Speckled ANA pattern with anti-Scl-70
d) Speckled ANA pattern with anti-SSB - Ankylosing spondylitis is strongly linked to:
a) HLA-DQ2
b) HLA-B27
c) HLA-DQ8
d) HLA-DR2 - A 54-year-old female smoker with fever, joint swelling, stiffness, high CRP, positive CCP, ANA (1:320, speckled), and negative RF most likely has:
a) Reactive arthritis
b) Rheumatoid arthritis
c) Systemic sclerosis
d) Sjögren syndrome - Which ANA pattern is associated with anti-dsDNA antibodies?
a) Rim (peripheral)
b) Speckled
c) Nucleolar
d) Centromere - A centromere ANA pattern is most often seen in:
a) Rheumatoid arthritis
b) Systemic lupus erythematosus
c) CREST syndrome
d) Sjögren syndrome - In indirect immunofluorescent ANA testing, a homogeneous pattern indicates antibodies to:
a) RNP
b) Sm
c) RNA
d) DNA - A speckled ANA pattern is typically associated with antibodies to:
a) Histone
b) Sm
c) RNA
d) DNA - Anti-RNA antibodies are usually linked with which ANA pattern?
a) Speckled
b) Rim
c) Diffuse
d) Nucleolar - Antibodies to extractable nuclear antigens usually give which ANA pattern?
a) Speckled
b) Rim
c) Diffuse
d) Nucleolar - A positive speckled ANA pattern should be followed by testing for:
a) Anti-mitochondrial antibodies
b) Immunoglobulin quantitation
c) Anti-Sm and anti-RNP antibodies
d) Anti-DNA by Crithidia assay - In the ANA test, HEp-2 cells fixed on slides act as:
a) Unlabeled antigen
b) Labeled antigen
c) Labeled antiglobulin
d) Unlabeled antiglobulin - Which thyroid antibody stimulates the TSH receptor, leading to hyperthyroidism?
a) Anti-thyroglobulin
b) Anti-thyroperoxidase
c) Anti-TSH receptor antibody (TRAb)
d) Anti-TSH - Rheumatoid factors are autoantibodies directed against:
a) Fc portion of IgG
b) Fab portion of IgG
c) J chain of IgM
d) Secretory component of IgA - In serological diagnosis, the presence of both IgM and IgG antibodies to the same pathogen usually indicates:
a) Past infection only
b) Recent or ongoing infection
c) No clinical relevance
d) False-positive result - A prozone effect in antibody testing occurs because of:
a) Excess antigen
b) Excess antibody
c) Lack of complement
d) Low incubation temperature - A patient suspected of having HIV shows a positive ELISA but a negative Western blot. The best interpretation is:
a) HIV infection confirmed
b) No infection, ELISA false-positive
c) Acute infection in window period
d) Need for viral load PCR - Which serological marker is most specific for systemic lupus erythematosus (SLE)?
a) ANA
b) Anti-dsDNA
c) Anti-RNP
d) Anti-SSA - A positive Monospot test is most consistent with:
a) Streptococcal pharyngitis
b) Infectious mononucleosis
c) Acute hepatitis B
d) HIV infection - The principle of latex agglutination tests is based on:
a) Antigen-antibody precipitation in gel
b) Antibodies or antigens bound to latex beads causing visible clumping
c) Enzyme-substrate reaction
d) Complement-mediated lysis - In hepatitis B infection, which marker indicates high infectivity?
a) Anti-HBs
b) HBsAg
c) HBeAg
d) Anti-HBc IgM - A rising ASO (anti-streptolysin O) titer indicates:
a) Past hepatitis B infection
b) Recent streptococcal infection
c) Autoimmune thyroid disease
d) Viral meningitis - The confirmatory test for syphilis after a reactive RPR is:
a) FTA-ABS
b) ANA
c) ASO
d) Cold agglutinin test - Which hepatitis serological profile indicates immunity from past infection?
a) HBsAg positive, Anti-HBs negative
b) Anti-HBs positive, Anti-HBc IgG positive
c) Anti-HBs positive, Anti-HBc negative
d) HBeAg positive - In flow cytometry, CD19 is a marker for:
a) T helper cells
b) B lymphocytes
c) NK cells
d) Monocytes - Which autoantibody is highly specific for rheumatoid arthritis?
a) ANA
b) Anti-CCP (cyclic citrullinated peptide)
c) Anti-Scl-70
d) Anti-dsDNA
📌 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) Serum
- b) Recent or acute infection
- b) Antibodies bound to red blood cells in vivo
- a) VDRL
- b) Acute infection
- c) IgG
- b) Cross-reactivity
- b) ELISA
- b) Western blot
- c) RPR
- b) Immunodiffusion
- b) Current HBV infection
- c) Immunity (past infection or vaccination)
- a) Agglutination of sheep RBCs
- b) Acute or chronic hepatitis C
- b) IgM
- b) Hemolysis is absent
- a) ELISA
- b) Rheumatoid factor (RF)
- b) Infectious mononucleosis
- c) Systemic lupus erythematosus (SLE)
- a) False negative result
- a) An antibody reacting with unrelated antigens
- b) Mycoplasma pneumoniae infection
- a) SLE
- c) FTA-ABS
- a) Acute rheumatic fever or glomerulonephritis
- b) Time between infection and detectable antibodies
- b) Infectious mononucleosis
- b) IgG
- b) Current or past infection
- b) Latex agglutination
- a) The highest dilution showing a positive reaction
- b) Parasitic infection or allergy
- b) Acute inflammation
- b) Fourfold rise in O or H antibodies
- c) Infectious mononucleosis
- c) Antibody in serum
- b) Negative result
- a) Hook effect
- b) Current acute HBV infection
- c) Immunofluorescence
- b) Active viral replication
- c) Donath-Landsteiner test
- b) Biological false-positive
- a) Paul-Bunnell test
- b) Western blot and ELISA
- b) Anti-thyroglobulin antibody test
- b) Immune deficiency evaluation
- a) Recent streptococcal infection
- b) Western blot
- c) Rheumatoid factor
- b) Anti-HBs
- a) Rickettsial infections
- Latex agglutination
- b) IgM antibodies
- c) RPR
- b) IgA
- a) Brucellosis
- b) Anti-dsDNA
- d) Anti-RNP antibody
- a) True positive cases correctly identified
- b) Serological antibody testing
- a) Thermal amplitude (temperature range)
- a) Overall complement system activity
- b) Human anti-mouse antibody (HAMA) activity
- a) 1072/μL
- c) Scatter light and emit fluorescence
- b) 1000/μL
- b) 60/μL
- a) T cell disorder
- a) Western blot
- d) RAST
- a) HBV DNA quantification by PCR
- c) IgM during acute illness and IgG rise during convalescence
- c) Hepatitis C
- a) Group A streptococcal infection
- a) Homogeneous ANA pattern with anti-dsDNA antibodies
- b) HLA-B27
- b) Rheumatoid arthritis
- a) Rim (peripheral)
- c) CREST syndrome
- d) DNA
- b) Sm
- d) Nucleolar
- a) Speckled
- c) Anti-Sm and anti-RNP antibodies
- a) Unlabeled antigen
- c) Anti-TSH receptor antibody (TRAb)
- a) Fc portion of IgG
- b) Recent or ongoing infection
- b) Excess antibody
- b) No infection, ELISA false-positive
- b) Anti-dsDNA
- b) Infectious mononucleosis
- b) Antibodies or antigens bound to latex beads causing visible clumping
- c) HBeAg
- b) Recent streptococcal infection
- a) FTA-ABS
- b) Anti-HBs positive, Anti-HBc IgG positive
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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