Week 2: Eias & Liason Flashcards
1
Q
Passive Immunity
A
Transfer of pre-formed antibodies to an unimmunized host
2
Q
Example of Naturally acquired passive immunity
A
passage of IgG from mom to fetus
3
Q
Example of artificially acquired passive immunity
A
injection of anti-serum; RhoGam, Hepatitis A
4
Q
Innate immunity
A
present at birth. Individuals ability to resist infection by normally present body functions
5
Q
Examples of innate immunity
A
phagocytic cells, complement, lysozymes in tears
6
Q
Adaptive immunity
A
developed after birth. Specificity to individual pathogens, ability to remember prior exposures and increases response upon repeat exposure.
7
Q
Example of adaptive immunity
A
Antibiodies
8
Q
Cell-mediated immunity
A
immunity dependent on the actions of T lymphocytes and macrophages/phagocytic cells
9
Q
Humoral Immunity
A
Immunity dependent on substances in serum
10
Q
Examples of humoral immunity
A
Antibodies and complement
11
Q
Vaccine
A
Suspension of killed or attenuated (inactivated) infectious agents administered to establish resistance to the disease
12
Q
Phases of the primary antibody response
A
- First exposure to antigen: cell-mediated or antibody production may be initiated/ Sometimes more than one exposure is needed
- Long lag phase where antibody production will not be detectable
- Slow increase in antibody titers
- A short plateau phase during which the antibody titer stabilizes
- A decline phase in which the antibody is catabolized
13
Q
How does one diagnose a current infection?
A
Positive IgM or a 4-fold rise in IgG
14
Q
What is the prozone phenomenon and what does it do?
A
Under the conditions of antibody excess, there exists a surplus of antibody binding sites that are not bound to antigenic determinants. Lattice formation is decreased because antigens only bind to one or two antibodies (no cross-linkage occurs).
15
Q
How does the prozone phenomenon affect test results?
A
A false negative can occur
16
Q
How can the prozone phenomena be overcome?
A
Serial-diluting the antibody-containing serum can overcome the phenomenon
17
Q
Sensitivity
A
Frequency of positive test results in patients with a particular disease - test’s ability to detect small concentrations
18
Q
Sensitivity calculation
A
[TP/(TP + FN)] x 100
19
Q
Specificity
A
Frequency of negative test results in patients without disease - degree of which the antibody reaction of it antigen is unique, the ability of a test to detect analyte as opposed to non-analyte
20
Q
Specificity calculation
A
[TN/(TN + FP)] x 100
21
Q
Advantages of ELISA over RIA
A
Comparable sensitivity without risk of health hazards, problems with disposal, or short shelf life
22
Q
Advantages of ELISA over IF/agglutination
A
Greater sensitivity, able to detect analytes that are small in size of low in concentration
23
Q
What is a conjugate?
A
Antibody that binds to the analyte and is labeled with a marker that allows the amount of antibody-antigen binding to be monitored
24
Q
Is ELISA used to measure antigen or antibody?
A
It can be used for either. It would depend on the assay design
25
When measuring patient antibody in a non-competitive solid-phase ELISA, how can the specific immunoglobulin class present be determined?
By using enzymes-labeled anti-immunoglobulin antibodies (AKA conjugate) that is specific for a single isotype or class of immunoglobulin.
26
Example of a conjugate?
IgM
27
Three assay performed in the SFMC immunology department that use ELISA
Toxoplasma IgM, PF4 IgG, H. pylori antigen, Giardia antigen, Cryptosporidium antigen
28
What are the desirable traits of an enzyme used in ELISA tests?
1. High turnover
2. Stability
3. Ease of conjugation
4. Lock of endogenous enzyme in patient sample
5. Ease of detection
6. Compatible with standard conditions used in ELISA
29
Two most popular enzymes used in ELISA test
Alkaline Phosphatase (AP) and Horseradish Peroxidase (HRP)
30
After completion of an ELISA test, the tech notes no color formation in any of the controls or patient tubes. What could be reasonable explanation of this?
Reagents were added out of order or omitted
31
How could result be affected by preparation of incorrect serum dilution?
If all calibrators, controls, and patients are diluted the same but incorrectly, all OD values will be affected similarly. Too much diluent in the tubes = all ODs would be lower than usual. Controls may or may not be in the range. We like to look at our calibrator OD values to see if they are about what they were previously
32
How could results be affected by expired positive control?
Positive control may be out of range (too low)
33
How could results be affected by conjugate and substrate added in reverse order?
No color formation in any wells
34
How could results be affected by one clogged tip on the wash-head?
May show up as one calibrator or control out of range. Issue can occur multiple runs if clog is not detected and fixed. Tech should watch washer action while priming to ensure all wash-heads are dispensing properly.
35
How could results be affected by washing the plate before adding the stop?
No color in any wells
36
Why do we put the regain bottles back into the refrigerator immediately after use?
Prolonged exposure to room temperature decreases the stability of the reagents
37
In what two forms does Giardia exist?
Trophozoite and Cyst
38
What is the difference between trophozoite and cyst giardia?
Trophozoite is non-infectious whereas cyst is highly infective
39
Trophozoite giardia morphology, survival, and inhabitant
pear shape, inhabits small intestines, survives only few hours outside body
40
Cyst giardia morphology and survival
elliptical shape, survives several days outside body
41
Giardia transmission
Water/food contamination
Travel to endemic areas
Direct contact with asymptomatic carriers
Sexual contact
42
Giardia symptoms
acute diarrhea, abdominal pain, malabsorption, weight loss
43
With what diseases can giardiasis be confused?
IBS, Crohn's, ulcerative colitis
44
What type of organisms is Cryptosporidium
Parasite
45
Cryptosporidium transmission
Direct contact with infected animals or people or from ingesting contaminated food/water
46
What group of people are at an increased risk of contracting Cryptosporidium?
HIV-infected patients
Day care center workers
Family members and sexual partners of infected patients
Travelers
47
What is the benefit of Cryptosporidium EIA over wet mount testing?
It is difficult to find the organism in a wet mount (May need modified acid-fast staining in order to visualize it all)
48
What invasive lab tests are available for the detection of infection with H. pylori?
Invasive techniques (collection of the gastric biopsies): Bacterial culture (gold standard), Histological staining, Rapid ureas)
49
What invasive lab tests are available for the detection of infection with H. pylori?
Invasive techniques (collection of the gastric biopsies): Bacterial culture (gold standard), Histological staining, Rapid urease)
50
What non-invasive lab tests are available for the detection of infection with H. pylori?
Urea breath test
Antibody detection EIA or latex agglutination
Antigen detection in stool via EIA
51
How is the urea breath test performed?
Patient ingests urea with isotope component; organism/urease breaks down urea and isotope detectable in breath
52
Why is a bacterial culture the gold standard for diagnosing H. pylori and what agars are needed?
It is fastidious to grow-will grow on chocolate agar but for selective media need a modified campy agar
53
what can negatively affect biopsy testing for H. pylori and why?
The patchy nature of the infection in the gut can negatively affect the sensitivity of biopsy testing
54
Describe the production of specific H. pylori's antibodies?
Antibodies appear to have little effect in eradication of the organism. In untreated individuals, specific IgG and IgA remain elevated. Post treatment, antibody level fall gradually over a period of many months, limiting the value of antibody testing in early post-treatment tracking
55
Why is an infection of H. pylori significant?
Primary cause of chronic gastritis. Associated with gastric and duodenal ulcers. Prolonged can risk gastric carcinoma and gastric mucosal-associated lymphoid tissue lymphoma
56
What type of organism is Toxoplasma gondii?
parasite
57
How can toxoplasma be transmitted to humans?
Eating raw or undercooked meat that contains T. gondii cysts, or ingesting food/water that has come into contact with contaminated meat
Ingesting oocytes present in cat feces
Transmission across the placenta from mother to fetus
58
In immunocompetent adults, is the toxoplasma infection symptomatic or asymptomatic?
Asymptomatic
59
How should serologically positive Toxoplasma results be followed up?
Toxoplasma-specific IgM in the newborn
60
Complications of fetal toxoplasmosis?
Miscarriage, still-birth, vision and hearing loss, stunted mental and psychomotor development, seizures, hepatosplenomegaly, hematological abnormalities
61
In toxoplasmosis how long can antibodies be detected by EIA after acute acquired infection?
18 months
62
Confirmatory testing in toxoplasmosis with positive IgG and IgM
avidity testing
63
What is platelet factor 4?
Platelet protein with high binding affinity for heparin
64
What clinical finding is seen when a patient has antibodies to platelet factor 4?
Thrombocytopenia (heparin-induced thrombocytopenia - HIT)
65
What other methods are available for testing for platelet factor 4?
Serotonin Release test and platelet aggregation
66
What is chemiluminescence?
The emission of light caused by a chemical reaction, typically and oxidation reaction, producing an excited molecule that decays back to its original ground state. The return from excited to ground state is what releases the light energy.
67
What is the principle of testing on the liaison and how does it work?
chemiluminescent immunoassay: chemiluminescent particle is conjugated to a monoclonal antibody. If the monoclonal antibody is bound to the antigen of interest, it remains in the test system where it is stimulated to release light energy. If the antigen is not present, the conjugate is washed away and the reaction does not occur
68
The CDC recommends what confirmatory test for Lyme disease if an EIA or IFA come back positive?
Western blot
69
What are the three stages for clinical manifestations in Lyme disease?
1. Early localization
2. Early dissemination
3. Late chronic
70
What occurs in the early localization stage of Lyme disease?
Erythema migraines (EMS) starts at bite site 2 days - 2 weeks post bite
Possible very mild flu-like symptoms
71
What occurs in the early dissemination stage of Lyme disease?
Arthritis in more than one joint, neurologic, cardiac, or other organ abnormalities
weeks-months post bite
72
What occurs in the late chronic stage of Lyme disease?
Persistence if symptoms in early dissemination disease more than 6-12 months
73
What other lab tests are currently available to aid in the diagnosis of Lyme disease?
Culture
PCR
Antibody detection ( EIFA, Immunoblot, ELISA)
Lymphocyte proliferative assays
74
Which immune response does the QFT-G plus test assess?
Cell-mediate immune response (type IV hypersensitivity)
75
Which antigen are present in the QFT tubes and what are their purpose?
ESAT-6, CFP-10, TB7.7.
76
Which mycobacteria cross react with the QFT-G plus assay?
M. kansasii, M. szulgai, M. marinum
77
Can a newly infected individual become ill from TB within weeks to months while most infected individuals remain well?
Yes
78
What is the term for a non-communicable asymptomatic conditions, persisting in some, who might develop TB disease months or year later and what is the main purpose of diagnosing this condition?
Latent TB. May want to consider medical treatment to prevent active TB
79
In the QFT-G Plus which protein in the antigen tubes are absent?
BCG
80
Disadvantages of the TST?
subjective reading of test
Foreign substance injected into skin
Requires 2 trips to the office
False positive secondary to vaccination with BCG, infection with other mycobacteria complex, pr other undetermined factors
False negative
81
Disadvantages of QFT-G IT assay?
High reagent cost to the lab
Tubes must be incubated within 16 hours of specimen collections then removed from incubator after 16-24 hours
Courier issues
82
Risk factors for TB?
Exposure to persons with TB
Employment in healthcare
Residence in congregate settings
Birth in a country with a high TB prevalence
Spending at least 2 cumulative month in a country with a high TB prevalence
83
Causes of indeterminate results of TB?
Poor washing
Use of other anticoagulants other than heparin
Incorrect transport
Excessive levels of circulating IFN
Immunosuppressive therapy
