Immunoassays - Questions based on Tutorial

Question 1

Which type of immunoassay interference involves substances that cause falsely increased results by blocking antibody binding?
A) Hormone binding proteins
B) Heterophile antibodies
C) Pre-analytical interference
D) Sample matrix effect

Answer 1

B) Heterophile antibodies

Question 2

What is the biggest potential clinical consequence of immunoassay interference?
A) Faster test result
B) Misdiagnosis and inappropriate treatment
C) Easier sample collection
D) Routine use in primary care

Answer 2

B) Misdiagnosis and inappropriate treatment

Question 3

Which type of antibody is most commonly responsible for heterophile interference in immunoassays?
A) Anti-human
B) Human anti-mouse antibody
C) Anti-dog
D) Rabbit anti-human

Answer 3

B) Human anti-mouse antibody (HAMA)

Question 4

What is the estimated percentage of documented interferences affecting cardiac or thyroid immunoassays?
A) Less than 5%
B) 10%
C) 45–50%
D) 80%

Answer 4

C) 45–50%

Question 5

Which immunoassay format is most commonly affected by the high-dose hook effect?
A) Competitive
B) Non-competitive sandwich assay
C) Immunodiffusion
D) Agglutination assays

Answer 5

B) Non-competitive sandwich assay

Question 6

What happens during the hook effect in immunometric (sandwich) assays?
A) Increased signal at high analyte concentration
B) Decreased signal at excessively high analyte concentration
C) No effect
D) Enhanced antibody specificity

Answer 6

B) Decreased signal at excessively high analyte concentration

Question 7

What intervention can minimize the high-dose hook effect in immunoassays?
A) Using higher sample volumes
B) Diluting the sample
C) Adding more patient sample
D) Removing labels

Answer 7

B) Diluting the sample

Question 8

Pre-analytical interferences can arise from:
A) Anticoagulants used in blood collection tubes
B) Incorrect sample storage
C) Delayed specimen processing
D) All of the above

Answer 8

D) All of the above

Question 9

How can hormone binding proteins interfere with immunoassay measurement?
A) By denaturing the analyte
B) By removing/binding analyte, leading to falsely low readings
C) By enhancing enzyme activity
D) No interference

Answer 9

B) By removing/binding analyte, leading to falsely low readings

Question 10

Which protein is specifically mentioned as an interfering hormone binding protein?
A) Insulin
B) Cortisol binding globulin
C) Thyroglobulin
D) Albumin

Answer 10

B) Cortisol binding globulin

Question 11

What is a common strategy to reduce hormone binding protein interferences?
A) Refrigerate samples
B) Add blocking agents or denature binding proteins
C) Increase sample volume
D) Change tube color

Answer 11

B) Add blocking agents or denature binding proteins

Question 12

Interference from autoanalyte antibodies most frequently affects which types of analytes?
A) Thyroid hormones
B) Enzymes like creatine kinase
C) Prolactin and testosterone
D) All of the above

Answer 12

D) All of the above

Question 13

Autoantibodies to thyroid hormones are typically seen in:
A) Diabetes
B) Hashimoto’s or Graves’ disease
C) Cushing’s syndrome
D) Iron deficiency anemia

Answer 13

B) Hashimoto’s or Graves’ disease

Question 14

Which immunoassay interference involves the sample matrix itself causing non-specific signal or inhibiting detection?
A) Cross-reactivity
B) Sample matrix effect
C) High-dose effect
D) Automation artifact

Answer 14

B) Sample matrix effect

Question 15

What can be done to address matrix effects in immunoassays?
A) Sample dilution
B) Matrix matching standard curves
C) Use of recovery experiments
D) All of the above

Answer 15

D) All of the above

Question 16

Pre-analytical factors include differences in analyte stability. Which hormone is specifically unstable in plasma?
A) ACTH
B) TSH
C) Insulin
D) Cortisol

Answer 16

A) ACTH

Question 17

ACTH remains stable in EDTA plasma at 4°C for:
A) 120 hours
B) 18 hours
C) 24 hours
D) 72 hours

Answer 17

B) 18 hours

Question 18

Which sample type can give different immunoassay results due to matrix interference?
A) Serum
B) Plasma
C) Urine
D) All of the above

Answer 18

D) All of the above

Question 19

What are common sources of heterophile antibody production in patients?
A) Animal workers
B) Monoclonal antibody therapy recipients
C) People exposed to mice
D) All of the above

Answer 19

D) All of the above

Question 20

Which immunoassay labels are most prone to interference by endogenous substances?
A) Fluorescent
B) Chemiluminescent
C) Enzyme-based
D) All of the above

Answer 20

D) All of the above

Question 21

Which is the best approach to minimize heterophile antibody interference?
A) Add animal serum or blocking reagent
B) Ignore interference
C) Use lower sample volumes
D) Replace with mass spectrometry

Answer 21

A) Add animal serum or blocking reagent

Question 22

Heterophile antibodies may cause falsely:
A) Increased results
B) Decreased results
C) Both
D) Neither

Answer 22

C) Both

Question 23

Automation in immunoassays can reduce which type of interference?
A) Human error in washing/separation steps
B) Reagent instability
C) Hook effect
D) Matrix effect

Answer 23

A) Human error in washing/separation steps

Question 24

What is a general sign of immunoassay interference in laboratory reports?
A) Results inconsistent with clinical picture
B) High accuracy
C) Acceptable precision
D) High sensitivity

Answer 24

A) Results inconsistent with clinical picture

Question 25

Cross-reactivity interference occurs when: A) Antibody binds unintended antigen B) Label is unstable C) Matrix effect present D) No wash step used

Answer 25

A) Antibody binds unintended antigen

Question 26

Which drug-induced antibodies may interfere with immunoassays? A) Anti-thyroid drugs B) Monoclonal antibodies given for therapy C) Beta blockers D) Steroids

Answer 26

B) Monoclonal antibodies

Question 27

Which cardiac marker is often affected by immunoassay interference? A) Troponin B) CK-MB C) BNP D) All of the above

Answer 27

D) All of the above

Question 28

What is a logical second step when immunoassay interference is suspected? A) Repeat assay with different platform B) Ignore the result C) Increase sample volume D) Use more enzyme label

Answer 28

A) Repeat assay with different platform

Question 29

Which immunoassay interference commonly leads to "undetectable" results in the presence of high analyte? A) High-dose hook effect B) Sample matrix C) Cross-reactivity D) Hemolysis

Answer 29

A) High-dose hook effect

Question 30

Which technique is emerging as a robust alternative where immunoassay interference is common? A) Liquid chromatography-mass spectrometry B) Immunodiffusion C) Western blot D) Flow cytometry

Answer 30

A) Liquid chromatography-mass spectrometry (LCMS)