Block B - Testing for Pregnancy

Question 1

What is the key hormone detected in modern pregnancy tests?
A) Estrogen
B) Progesterone
C) hCG
D) Luteinizing Hormone (LH)

Answer 1

C, hCG

Question 2

Which pregnancy test method involves latex beads coated with hCG?
A) Radioimmunoassay (RIA)
B) Inhibition of Latex Agglutination (ILA)
C) Dip-stick test
D) ELISA

Answer 2

B

Question 3

Why was the rabbit test for pregnancy unreliable?
A) It was slow and required killing the animal
B) It did not detect hCG
C) It had a high false-positive rate
D) It could only detect late pregnancy

Answer 3

A

Question 4

What is the advantage of radioimmunoassay (RIA) over latex agglutination for pregnancy testing?
A) RIA is quantitative and highly sensitive
B) RIA does not require antibodies
C) RIA is cheaper and faster
D) RIA is a non-immunoassay method

Answer 4

A

Question 5

Why do dip-stick pregnancy tests have two lines?
A) One line detects hCG, the other is a control
B) One line confirms fertilization, the other confirms implantation
C) The first line detects progesterone, the second detects hCG
D) One line appears only in early pregnancy

Answer 5

A

Question 6

Which type of immune cells does HIV primarily infect?
A) CD8+ T cells
B) B cells
C) CD4+ T cells
D) Macrophages

Answer 6

C

Question 7

What is the purpose of flow cytometry in HIV monitoring?
A) To detect viral RNA
B) To quantify CD4+ T cell counts
C) To measure hCG levels
D) To diagnose acute infections

Answer 7

B

Question 8

What does side scatter (SS) in flow cytometry measure?
A) Cell size
B) Cell complexity and granularity
C) Cell fluorescence
D) Cell density

Answer 8

B

Question 9

What is the key marker for T-helper cells in flow cytometry?
A) CD3+
B) CD8+
C) CD4+
D) CD19+

Answer 9

C

Question 10

Why is flow cytometry preferred over fluorescent microscopy for HIV monitoring?
A) It is faster and more automated
B) It detects HIV viral proteins
C) It can detect cytokines
D) It requires fewer samples

Answer 10

A

Question 11

What is the main difference between RIST and RAST tests for allergy?
A) RIST detects total IgE, RAST detects specific IgE
B) RIST is qualitative, RAST is quantitative
C) RIST detects allergens, RAST detects antibodies
D) RIST is more sensitive than RAST

Answer 11

A

Question 12

What type of immunoassay is used in RAST tests?
A) Fluorescent Polarization Immunoassay (FPIA)
B) Radioimmunoassay (RIA)
C) Latex Agglutination Test
D) Dip-stick test

Answer 12

B

Question 13

What happens in passive cutaneous anaphylaxis when an allergic reaction occurs?
A) IgG binds to allergens and activates mast cells
B) IgE binds to mast cells, causing histamine release
C) T cells attack allergens
D) B cells produce cytokines

Answer 13

B

Question 14

What is the main principle of Fluorescence Polarization Immunoassay (FPIA)?
A) Fluorescent-labeled drugs rotate freely when unbound
B) Antigens and antibodies react to produce agglutination
C) Radioactive hCG binds to antibodies
D) Cell size and granularity are measured

Answer 14

A

Question 15

Which of the following drugs is commonly monitored using FPIA?
A) hCG
B) Digoxin
C) Insulin
D) Estrogen

Answer 15

B

Question 16

What are the three main types of pregnancy immunoassays?

Answer 16

-Inhibition of Latex Agglutination (ILA) – clinical use
-Radioimmunoassay (RIA) – highly sensitive, uses radioactivity
-Dip-stick (Lateral Flow Assay) – home & clinical, visual detection

Question 17

How does a dip-stick pregnancy test work? (3 marks)

Answer 17

-Anti-hCG antibodies on latex beads bind hCG in urine.
-The beads travel up the filter and bind immobilized anti-hCG, forming a colored line.
-A second line binds anti-rabbit IgG as a control.

Question 18

What does flow cytometry measure in HIV patients? (3 marks)

Answer 18

-CD4+ T cell counts – key for tracking HIV progression.
-Forward scatter (FS) – cell size.
-Side scatter (SS) – granularity & complexity.

Question 19

How do RIST and RAST tests differ?

Answer 19

RIST = Measures total IgE (overall allergy response).
RAST = Measures specific IgE (identifies allergens)

Question 20

What principle does Fluorescence Polarization Immunoassay (FPIA) use? (3 marks)

Answer 20

-Measures drug concentration in serum.
-High drug levels = More unbound drug → low fluorescence polarization.
-Low drug levels = More bound drug → high fluorescence polarization.

Question 21

Why is FPIA preferred over ELISA for therapeutic drug monitoring?
A) FPIA is homogeneous, eliminating the need for separation steps.
B) ELISA requires more patient blood volume for testing.
C) ELISA is less specific than FPIA for small molecules.
D) FPIA can measure large and small molecules equally well.

Answer 21

A because FPIA is faster and requires fewer wash steps than ELISA because it does not require antigen immobilization.

Question 22

A patient on digoxin therapy has low blood digoxin levels despite taking their prescribed dose. What could explain this?
A) The patient is metabolizing digoxin too quickly due to drug interactions.
B) The test is detecting a different cardiac glycoside, giving a false result.
C) The patient has developed antibodies against digoxin, making it undetectable.
D) The digoxin assay is not sensitive enough to measure therapeutic levels.

Answer 22

A, Rifampin and St. John’s Wort increase digoxin metabolism, lowering levels.

Question 23

Why does Fluorescence Polarization Immunoassay (FPIA) work best for small molecules like drugs?
A) Small molecules rotate more freely in solution, affecting fluorescence polarization.
B) Large molecules absorb too much light, interfering with detection.
C) Large molecules bind antibodies too strongly, preventing accurate competition.
D) Small molecules fluoresce more efficiently than larger ones.

Answer 23

A, The degree of rotation of a fluorescently labeled molecule depends on its size. More rotation = lower polarization.

Question 24

Why might immunotherapy (allergy shots) shift antibody production from IgE to IgG?
A) Repeated exposure to the allergen promotes IgG4 production, which blocks mast cell activation.
B) IgG is more stable in the blood, so it outcompetes IgE.
C) IgG directly destroys allergens through complement activation.
D) The therapy suppresses the immune system, reducing IgE production.

Answer 24

A, IgG4 acts as a “blocking antibody” that prevents allergens from cross-linking IgE on mast cells, reducing allergic responses.

Question 25

A patient has high total IgE levels but negative RAST results for all tested allergens. What does this suggest? A) The patient may have a non-allergic condition that elevates IgE, like parasitic infection. B) The test was performed incorrectly and should be repeated. C) The patient has a very mild allergy that is undetectable by current tests. D) The patient has an autoimmune disease affecting IgE production.

Answer 25

A, Parasitic infections (e.g., helminths) and chronic diseases (e.g., hyper-IgE syndrome) can elevate total IgE without an allergic reaction.

Question 26

In flow cytometry, why is it important to use multiple fluorescent markers when analyzing immune cells? A) It allows identification of distinct immune cell subsets based on surface markers. B) It increases the total fluorescence detected, improving accuracy. C) It prevents antibody cross-reactivity and non-specific binding. D) It improves light scattering and reduces autofluorescence.

Answer 26

A, CD3+CD4+ identifies helper T cells, CD3+CD8+ identifies cytotoxic T cells.

Question 27

A patient with suspected HIV infection has a normal CD4+ T cell count but tests positive for viral RNA. What is a possible explanation? A) The patient is in the acute stage of HIV infection before significant CD4+ depletion. B) The patient has a CD4 mutation that makes their cells resistant to HIV. C) The flow cytometry results are incorrect, and the test should be repeated. D) The viral RNA test is detecting an unrelated virus.

Answer 27

A, Acute HIV (seroconversion phase) often shows high viral load but no CD4 drop yet.

Question 28

Could a dip-stick pregnancy test work if an hCG mutant was produced that lacked the beta-subunit? Why or why not? A) No, because current tests target the unique beta-subunit of hCG. B) Yes, because the alpha-subunit is still recognized by antibodies. C) No, because the mutant hCG would not be present in urine. D) Yes, because any form of hCG will bind to anti-hCG antibodies.

Answer 28

A, The alpha-subunit of hCG is shared with LH, FSH, and TSH, so pregnancy tests target β-hCG for specificity.

Question 29

Why do some pregnancy tests produce false positives in women with trophoblastic diseases or certain cancers? A) Cancer cells can produce hCG or structurally similar molecules. B) The immune system reacts to cancer by producing antibodies that mimic hCG. C) These conditions interfere with the colorimetric reaction in dip-stick tests. D) The test detects progesterone instead of hCG.

Answer 29

A, Choriocarcinoma, testicular cancer, and molar pregnancies can elevate hCG.

Question 30

A woman takes a home pregnancy test, and the test line appears faint. What could explain this? A) She is very early in pregnancy and has low hCG levels. B) The test is defective and should be discarded. C) The woman is not pregnant, but the test is reacting to progesterone. D) The test is an antigen-based assay and should be repeated using RIA.

Answer 30

A, A faint line can also occur due to diluted urine (low concentration of hCG) or an evaporation line.

Question 31

Which of the following historical pregnancy tests involved injecting urine into immature mice or rats? A) Frog test B) A-Z test (Aschheim-Zondek test) C) Hemagglutination inhibition test D) Radioimmunoassay

Answer 31

B) A-Z test (Aschheim-Zondek test)

Question 32

Which pregnancy test method is used in home pregnancy kits? A) Radioimmunoassay B) Inhibition of latex agglutination C) Dip-stick lateral flow assay D) ELISA

Answer 32

C) Dip-stick lateral flow assay

Question 33

What is a limitation of Radioimmunoassay (RIA) for pregnancy testing? A) It cannot be automated. B) It has low sensitivity. C) It produces radioactive waste. D) It is slower than traditional biological assays.

Answer 33

C) It produces radioactive waste.

Question 34

What is the primary advantage of digital pregnancy tests over traditional dip-stick tests? A) They do not rely on immunoassays. B) They detect progesterone instead of hCG. C) They use a spectrophotometer to quantify hCG concentration. D) They require laboratory analysis.

Answer 34

C) They use a spectrophotometer to quantify hCG concentration.

Question 35

Which immune cell population is monitored using flow cytometry to track HIV progression? A) CD8+ T cells B) B cells C) CD4+ T cells D) Natural Killer (NK) cells

Answer 35

C) CD4+ T cells

Question 36

What does forward scatter (FS) in flow cytometry indicate? A) Cell granularity B) Cell size C) Cell fluorescence D) Antibody concentration

Answer 36

B) Cell size

Question 37

Which marker is used to differentiate helper T cells from other T cells in flow cytometry? A) CD3 B) CD8 C) CD4 D) CD19

Answer 37

C) CD4

Question 38

What is the major limitation of fluorescence microscopy compared to flow cytometry in HIV monitoring? A) It requires expensive lasers. B) It can only count a small number of cells and is operator-dependent. C) It cannot detect HIV infection. D) It cannot be used to quantify T cell subsets.

Answer 38

B) It can only count a small number of cells and is operator-dependent.

Question 39

What does RIST (Radioimmunosorbent Test) measure? A) Total IgE levels B) Specific IgE to allergens C) Total IgG levels D) Histamine concentration

Answer 39

A) Total IgE levels

Question 40

What is a major limitation of RIST compared to RAST? A) It is more expensive. B) It only provides total IgE levels, not allergen-specific IgE. C) It requires live animals for testing. D) It cannot be used for industrial allergy screening.

Answer 40

B) It only provides total IgE levels, not allergen-specific IgE.

Question 41

What is the primary advantage of cytometric bead arrays (CBAs) over traditional RAST for allergy testing? A) CBAs use fluorescent beads instead of radioactivity. B) CBAs detect total IgE only. C) CBAs require larger sample volumes. D) CBAs have lower sensitivity.

Answer 41

A) CBAs use fluorescent beads instead of radioactivity.

Question 42

What is the principle of Fluorescence Polarization Immunoassay (FPIA)? A) Large fluorescent molecules rotate faster than small molecules. B) Small fluorescent molecules rotate faster than large molecules. C) Fluorescence is absorbed by unbound drug molecules. D) Polarization is increased when the drug is free in solution.

Answer 42

B) Small fluorescent molecules rotate faster than large molecules.

Question 43

Why is FPIA preferred for small molecules like drugs? A) It is a competitive immunoassay. B) Small molecules fluoresce more efficiently. C) Large molecules do not rotate freely, making polarization effects unreliable. D) It only works for molecules over 50,000 Da.

Answer 43

C) Large molecules do not rotate freely, making polarization effects unreliable.

Question 44

Describe the three immunoassay-based pregnancy tests and explain their advantages/disadvantages.

Answer 44

-Inhibition of Latex Agglutination (ILA) → Clinical use, qualitative, time-consuming. -Radioimmunoassay (RIA) → Clinical, quantitative, highly sensitive, but radioactive waste. -Dip-stick lateral flow assay → Home & clinical, fast, easy, but not quantitative.

Question 45

Why might a pregnancy test be positive in a non-pregnant individual? (3 marks)

Answer 45

Ectopic pregnancy Trophoblastic tumors (e.g., choriocarcinoma) Incomplete miscarriage

Question 46

Explain how flow cytometry is used to monitor HIV progression. (3 marks)

Answer 46

-CD4+ T cell enumeration -Fluorescent antibodies against CD3/CD4 -Stages of HIV progression (Acute, Chronic, AIDS)

Question 47

What is the significance of a low CD4/CD8 ratio in HIV patients? (3 marks)

Answer 47

-A low ratio suggests immune suppression -Indicates progression toward AIDS -Can be used to track ART (antiretroviral therapy) effectiveness

Question 48

Compare and contrast RIST vs. RAST in allergy testing. (3 marks)

Answer 48

RIST = Measures total IgE, good for diagnosing atopy but not specific allergens. RAST = Measures specific IgE, used for identifying allergens.

Question 49

What are the advantages of fluorescent bead arrays over RAST? (3 marks)

Answer 49

-Detect multiple allergens at once -No radioactivity required -Higher sensitivity & specificity

Question 50

Explain why FPIA is better suited for drug monitoring than ELISA. (3 marks)

Answer 50

-Faster & requires no wash steps -Homogeneous assay (no separation needed) -High sensitivity for small drugs like digoxin

Question 51

A patient with suspected ectopic pregnancy tests negative on a home pregnancy test but has mildly elevated hCG in a clinical blood test. What is the most likely explanation? A) The dip-stick test is faulty and should be discarded. B) The patient’s urine hCG levels are too low for detection. C) The patient has an undetectable pregnancy due to rapid metabolism of hCG. D) The presence of heterophile antibodies interfered with the dip-stick assay.

Answer 51

B) The patient’s urine hCG levels are too low for detection.

Question 52

Which of the following would NOT cause a false-positive result in an hCG-based pregnancy test? A) Trophoblastic tumors (e.g., choriocarcinoma) B) Excess luteinizing hormone (LH) production C) Recent miscarriage D) High progesterone levels due to ovarian cysts

Answer 52

D) High progesterone levels due to ovarian cysts.

Question 53

What is a major flaw in traditional hemagglutination inhibition pregnancy tests? A) They are highly sensitive but slow. B) They cannot differentiate hCG from LH. C) They require radioactive labeling. D) They use monoclonal antibodies, which lower specificity.

Answer 53

B) They cannot differentiate hCG from LH.

Question 54

A patient undergoing antiretroviral therapy (ART) has a stable CD4+ count but a worsening CD4/CD8 ratio. What does this indicate? A) The treatment is effective, and the patient is recovering. B) CD8+ T cells are increasing, suggesting immune activation or co-infection. C) Flow cytometry results are unreliable in HIV patients. D) The patient’s CD4+ T cells are being replaced by B cells.

Answer 54

B) CD8+ T cells are increasing, suggesting immune activation or co-infection.

Question 55

Why is flow cytometry preferred over ELISA for tracking HIV progression? A) ELISA cannot quantify absolute CD4+ T cell counts. B) Flow cytometry detects HIV RNA, while ELISA does not. C) Flow cytometry is cheaper and requires less expertise than ELISA. D) ELISA is used for antibody detection, which is not useful for monitoring disease progression.

Answer 55

A) ELISA cannot quantify absolute CD4+ T cell counts.

Question 56

Which of the following would most likely compromise the accuracy of a CD4+ T cell count measured via flow cytometry? A) Use of fluorochrome-labeled monoclonal antibodies B) Improper gating strategy leading to inclusion of non-CD4+ lymphocytes C) Low side scatter (SSC) settings, increasing cell granularity detection D) Use of forward scatter (FSC) to exclude non-lymphoid cells

Answer 56

B) Improper gating strategy leading to inclusion of non-CD4+ lymphocytes.

Question 57

A patient with high total IgE (RIST test positive) but negative RAST results for all allergens likely has: A) A parasitic infection or a non-allergic cause of IgE elevation. B) Severe anaphylaxis to an unidentified allergen. C) A RAST test error requiring repeat testing. D) A local allergic response that is only detectable in skin tests.

Answer 57

A) A parasitic infection or a non-allergic cause of IgE elevation.

Question 58

What is a major advantage of cytometric bead arrays (CBAs) over traditional RAST tests in allergy diagnosis? A) CBAs measure multiple allergens simultaneously using fluorescence-based detection. B) CBAs detect total IgE levels, while RAST does not. C) CBAs require radioactive labeling for increased sensitivity. D) CBAs are less sensitive than RAST but more specific.

Answer 58

A) CBAs measure multiple allergens simultaneously using fluorescence-based detection.

Question 59

Which of the following could cause a false negative in an allergy skin prick test? A) Patient has high circulating IgE levels. B) Patient is taking antihistamines. C) Test was performed on the forearm instead of the back. D) Patient has an autoimmune condition.

Answer 59

B) Patient is taking antihistamines.

Question 60

Why is FPIA best suited for monitoring small molecule drugs like digoxin? A) Small molecules rotate freely in solution, affecting fluorescence polarization. B) Large molecules have higher fluorescence intensity, making them difficult to detect. C) Large molecules outcompete the fluorescent-labeled drug, reducing accuracy. D) FPIA requires a high molecular weight antigen for proper function.

Answer 60

A) Small molecules rotate freely in solution, affecting fluorescence polarization.

Question 61

A patient taking biotin supplements shows abnormally low thyroid hormone levels in an ELISA-based TSH assay. What is the most likely explanation? A) Biotin interferes with streptavidin-biotin capture systems used in sandwich ELISA. B) Biotin directly inhibits TSH production in the thyroid. C) Biotin causes cross-reactivity between TSH and hCG. D) The patient’s actual TSH levels are too high for detection.

Answer 61

A) Biotin interferes with streptavidin-biotin capture systems used in sandwich ELISA.

Question 62

A patient presents with symptoms of pregnancy, but repeated dip-stick tests are negative. A quantitative ELISA for hCG shows a value of 5 mIU/mL, just at the detection threshold for pregnancy. What would you recommend next? A) Perform a radioimmunoassay (RIA) to confirm the result. B) Repeat the dip-stick test with a different brand. C) Wait 48 hours and repeat the quantitative hCG test. D) Test for progesterone levels, as hCG is unreliable.

Answer 62

C) Wait 48 hours and repeat the quantitative hCG test.

Question 63

A patient with advanced HIV infection has a low CD4+ count as measured by flow cytometry, but an unusually high total lymphocyte count. The clinician suspects an error in the gating strategy. What could explain this discrepancy? A) The forward scatter (FS) setting was too high, excluding some CD4+ T cells. B) The side scatter (SS) setting mistakenly included granulocytes, inflating total lymphocyte counts. C) There was nonspecific antibody binding, leading to false detection of CD4+ cells. D) The sample contained dead or apoptotic cells, artificially lowering CD4+ counts.

Answer 63

D) The sample contained dead or apoptotic cells, artificially lowering CD4+ counts.

Question 64

A flow cytometry analysis of an HIV-positive patient shows unexpectedly high CD4/CD8 ratio, even though the patient has worsening symptoms. What is the best course of action? A) Perform a repeat flow cytometry test with a fresh blood sample. B) Confirm HIV progression using a plasma viral load (HIV RNA PCR) test. C) Assume the patient has recovered and stop ART (antiretroviral therapy). D) Perform a Western blot to confirm HIV status.

Answer 64

B) Confirm HIV progression using a plasma viral load (HIV RNA PCR) test.

Question 65

A patient with a history of severe allergic reactions undergoes RAST testing for specific IgE antibodies to various allergens. All tests return negative, yet the patient continues to experience anaphylaxis upon peanut exposure. What is the most likely explanation? A) The patient has a non-IgE mediated allergy (e.g., food protein-induced enterocolitis syndrome). B) The RAST test was performed incorrectly and should be repeated. C) The patient is not allergic, and their symptoms are due to psychosomatic factors. D) The RAST test had too low sensitivity to detect IgE at clinically relevant levels.

Answer 65

A) The patient has a non-IgE mediated allergy (e.g., food protein-induced enterocolitis syndrome).

Question 66

A company develops a new microarray-based allergy test that detects hundreds of allergens in a single assay. However, it shows higher false-positive rates than traditional RAST. What could explain this? A) The test uses fluorescent beads, which are less accurate than radioimmunoassays. B) The increased sensitivity of microarrays picks up low-affinity IgE, which may not be clinically relevant. C) The test cannot differentiate IgG from IgE, leading to cross-reactivity. D) The test requires larger blood samples, which increases errors.

Answer 66

B) The increased sensitivity of microarrays picks up low-affinity IgE, which may not be clinically relevant.

Question 67

A patient on digoxin therapy has normal blood drug levels when measured by FPIA, yet they exhibit signs of digoxin toxicity (nausea, arrhythmias). What could be causing this? A) The patient has anti-digoxin antibodies, which interfere with FPIA detection. B) The patient’s kidney function has improved, causing drug accumulation. C) The patient is metabolizing digoxin too quickly. D) The FPIA method underestimates digoxin concentrations due to low drug polarity.

Answer 67

A) The patient has anti-digoxin antibodies, which interfere with FPIA detection.

Question 68

A hospital laboratory finds inconsistent results between ELISA-based and fluorescence polarization immunoassay (FPIA) for therapeutic drug monitoring of theophylline. What is the most likely reason? A) FPIA is a competitive assay, while ELISA is a sandwich assay, leading to different sensitivities. B) ELISA requires radioactive labels, which degrade over time. C) FPIA is more affected by sample viscosity, altering drug-antibody binding. D) ELISA has higher fluorescence interference, leading to overestimation of drug levels.

Answer 68

A) FPIA is a competitive assay, while ELISA is a sandwich assay, leading to different sensitivities.

Question 69

What is the primary reason why home dip-stick pregnancy tests use monoclonal antibodies? A) Monoclonal antibodies provide higher specificity for detecting hCG. B) Monoclonal antibodies allow for cross-reactivity with LH and FSH. C) Polyclonal antibodies are too expensive to use in home pregnancy tests. D) Monoclonal antibodies react better with progesterone than polyclonal antibodies.

Answer 69

A) Monoclonal antibodies provide higher specificity for detecting hCG, targeting specific epitopes of hCG, reducing false positives from LH or FSH.

Question 70

Which immunoassay method for pregnancy testing is most appropriate for clinical use when a precise hCG concentration is required? A) Dip-stick lateral flow assay B) Inhibition of latex agglutination test C) Radioimmunoassay (RIA) D) Wine-mixing test

Answer 70

C) Radioimmunoassay (RIA)

Question 71

What is a major disadvantage of inhibition of latex agglutination tests for pregnancy detection? A) They require radiolabeled antibodies. B) They are time-consuming and depend on visual interpretation. C) They are only useful for detecting progesterone. D) They produce high levels of false positives.

Answer 71

B) They are time-consuming and depend on visual interpretation.

Question 72

Flow cytometry is commonly used to monitor HIV progression by tracking: A) Viral RNA load in the bloodstream B) CD4+ T cell counts in blood samples C) Anti-HIV antibody levels D) Cytokine production by macrophages

Answer 72

B) CD4+ T cell counts in blood samples.

Question 73

Which factor can interfere with the accuracy of CD4+ T cell enumeration in flow cytometry? A) Using monoclonal antibodies specific for CD8+ instead of CD4+ B) Incorrect gating of lymphocyte populations C) Use of fluorochromes with high quantum yield D) Performing flow cytometry on plasma instead of whole blood

Answer 73

B) Incorrect gating of lymphocyte populations.

Question 74

A hospital lab finds that CD4+ T cell counts are consistently lower than expected in patients undergoing HIV treatment. Which of the following is the most likely cause of error? A) Overestimation of CD8+ T cells due to poor antibody specificity B) Use of old blood samples, leading to cell degradation C) Incorrectly adjusting forward scatter (FS) settings D) Using too many fluorescent labels, leading to signal quenching

Answer 74

B) Use of old blood samples, leading to cell degradation.

Question 75

A patient undergoes RIST and RAST testing. Their RIST result is high, but all RAST tests for specific allergens are negative. What is the most likely interpretation? A) The patient has an autoimmune disease. B) The patient has elevated total IgE but no specific IgE for common allergens. C) The RIST test was performed incorrectly. D) The patient is not allergic and should undergo immunotherapy.

Answer 75

B) The patient has elevated total IgE but no specific IgE for common allergens.

Question 76

What is the main advantage of cytometric bead arrays (CBAs) over traditional RAST tests? A) CBAs can detect multiple allergens simultaneously. B) CBAs require fewer antibodies for allergen detection. C) CBAs do not require fluorescent labeling. D) CBAs can directly quantify total IgE levels.

Answer 76

A) CBAs can detect multiple allergens simultaneously.

Question 77

Why is fluorescence polarization immunoassay (FPIA) particularly useful for monitoring small molecule drugs like digoxin? A) It does not require washing steps, making it fast and efficient. B) It works only for large proteins, making it highly specific. C) It does not rely on competitive binding assays. D) It detects fluorescently labeled drugs bound to albumin.

Answer 77

A) It does not require washing steps, making it fast and efficient.

Question 78

A hospital uses ELISA for monitoring theophylline levels, but results show high variability. Why might FPIA be a better alternative? A) FPIA is less sensitive, reducing false positives. B) FPIA has faster turnaround time and is automated. C) ELISA is only suitable for hormone detection. D) ELISA does not work with competitive binding assays.

Answer 78

B) FPIA has faster turnaround time and is automated.

Question 79

A patient on digoxin therapy has normal blood drug levels by FPIA, yet shows signs of toxicity (arrhythmias, nausea). What is the most likely explanation? A) The patient has kidney failure, leading to drug accumulation. B) The patient’s digoxin metabolites interfere with FPIA results. C) The FPIA test was contaminated. D) The digoxin antibody used in FPIA is too sensitive, causing false negatives.

Answer 79

B) The patient’s digoxin metabolites interfere with FPIA results.