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Serology > Routine bench > Flashcards

Routine bench Flashcards

1
Q

Carriers used in agglutination testing

A

Erythrocytes, bacterial cells, inert carriers like latex

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2
Q

Factors that can influence the mechanism of agglutination

A

pH, length of incubation, ionic strength, temperature, stearic hinderance, zeta potential

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3
Q

Hemagglutination

A

detects antibodies to erythrocyte antigens

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4
Q

Indirect/passive hemagglutination

A

detects antibodies to antigens other than on RBCs. Chemicals like chromic chloride, tannic acid and glutaraldehyde can be used to cross-link antigens to the cells.

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5
Q

PM shift collects red and lav top tubes and puts them in the refrigerator with the serology RPR specimens. Why are they now unacceptable for cold agglutinin testing?

A

Storage at 4 Celsius will result in absorption of the cold agglutinins onto the RBCs. They will be absent from the serum and cause a false negative

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6
Q

A physician orders a cold agglutinin titer and states that the patient had electrolytes ordered that morning. When you get the patient’s serum from Chemistry and get a random lav top from hemo for the cells. Your titer shows a strong, irreversible agglutination in tubes 1-11 and a negative result in 12. Why did this occur?

A

The cells from the lav top were ABO incompatible with the patient. Tube 12 is a negative control with no serum.

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7
Q

Prozone reaction and appearance in cold agglutinin test

A

Antibody concentration is greater than that of the antigen so the precipitate may be diminished or absent. The first few tubes would show no agglutination until higher dilutions.

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8
Q

Why are 2 different latex reagents used in the cryptococcus assay?

A

If only the detection latex is positive, it is a true positive. If the control latex is positive, there is a nonspecific interfering factor

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9
Q

How is cryptococcal infection usually acquired?

A

Inhalation of fungus into lungs. Associated with aged bird droppings and soils contaminated with these droppings.

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10
Q

What other lab methods are used in the diagnosis of cryptococcal infection?

A

Fungus culture, microscopic examination, IFA, complement fixation, skin test

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11
Q

What does out CALAS test detect?

A

capsular polysaccharide antigens of Cryptococcus neoformans in serum and CSF

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12
Q

Why and how is complement inactivated in body fluids prior to testing?

A

Complement is known to interfere with the reactions of certain tests. Inactivation is the process that destroys complement activity.
Serum = add pronase and place in 56 Celsius water bath from 15 minutes then boil for 5 minutes
CSF = boil for 5 minutes

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13
Q

Heterophile antibody

A

Heterophile antibodies are produced in response to 1 antigen but will react with an unrelated surface antigen present on cells from different mammalian species

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14
Q

Which heterophile antibody is associated with infectious mononucleosis? Is it absorbed by guinea pig kidney cells or by beef erythrocytes? Why is this important?

A

Paul-Bunnell heterophile antigen occurs in IM and is absorbed by beef erythrocytes. It differentiates is from heterophile antibodies found in conditions like serum sickness and rheumatic diseases absorbed by kidney cells

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15
Q

What principle is our Sure-Vue heterophile antibody test based on?

A

Davidsohn Differential test

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16
Q

What population is at a greater rick of developing mono?

A

In developed countries EBV is seen in adolescence and is symptomatic in older children and adults. In developing countries EBV is seen in early childhood and is asymptomatic

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17
Q

What other organisms can cause an IM-like illness?

A

CMV, toxoplasma, HIV, adenovirus, rubella. A majority of IM come from an unknown etiology

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18
Q

When do IM heterophile antibody levels peak?

A

2-3 weeks of infection

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19
Q

What immunoglobulin class is the IM heterophile antibody?

A

IgM

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20
Q

What hematological findings is often present with IM?

A

Atypical/reactive lymphocytes

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21
Q

How is flocculation different from agglutination?

A

Flocculation is a specific type of precipitation that occurs over a normal range of antigen concentration. It has a fine precipitate that stays suspended. Agglutination has an insoluble antigen.

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22
Q

What kind of test is the RPR?

A

Flocculation

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23
Q

5 components of RPR antigen and their function

A

Cardiolipin = antigenic component, phospholipid from beef heart
Cholesterol = increase solubility
Lecithin = increase sensitivity and standardize the reaction
Choline chloride = eliminates the need to heat inactivate serum, inactivates the complement
Charcoal = visualizing agent, particles entrapped in Ag-Ab lattice, macroscopic reading

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24
Q

Differences between antigen used in RPR and VDRL tests

A

Complement inactivation = RPR has choline chloride, VDRL doesn’t
Visualization = RPR uses charcoal (macroscopic reading), VDRL doesn’t (microscopic reading)

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25
Q

RPR vs Syphilis IgG test specificity and sensitivity

A

RPR = nonspecific, detect reagin on antibody like substance present in syphilis and variety of other diseases, non-treponemal
IgG = specific, detects anti-treponemal antibodies, the antigen is treponemal pallidum subspecies pallidum.
Sensitivity is almost equal

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26
Q

What must be done to rotator before rotating cards?

A

Make sure speed is 100 RPM

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27
Q

Describe some important details concerning the use of the RPR antigen needle

A

Check delivery of new needle 60 drops/1 mL
Needle should be free of bubble when dispensing drops
Don’t wipe needle
Rinse with CLRW daily

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28
Q

Primary syphilis and RPR, FTA-ABS and CSF-VDRL

A

pos RPR, pos FTA, NR VDRL (not usually preformed)

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29
Q

Secondary syphilis and RPR, FTA-ABS and CSF-VDRL

A

pos RPR, pos FTA, NR VDRL (not usually preformed)

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30
Q

Tertiary syphilis and RPR, FTA-ABS and CSF-VDRL

A

Pos or NR RPR, pos FTA, pos if neurosyphilis VDRL

31
Q

Treated syphilis and RPR, FTA-ABS and CSF-VDRL

A

NR RPR, pos FTA, NR VDRL

32
Q

2 most common methods for direct detection of T. pallidum

A

Dark field microscopy and fluorescent antibody testing

33
Q

Why are serologic tests for syphilis performed rather than direct detection of organism by culture?

A

Cannot be readily isolated or sustained in all culture. Not available in latent or tertiary stages because there is no lesions

34
Q

reactivity in RPR

A

Reactivity level of various treponemal tests may differ because of variation in antigen prep. Success of treatment is based on a 4-fold decrease in titer. Same tests used initially should also be used to monitor treatment.

35
Q

Principle of the immunodiffusion fungal antibody test

A

Antibody and soluble antigen are placed in separate wells of diffusion medium and allowed to diffuse outward into the medium. Between the wells, a concentration gradient of each of the components is established ranging from antigen excess to antibody excess. Visual line of precipitate forms at point of equivalence

36
Q

What is the predominant limitation of the fungal procedure?

A

Cross reaction between fungi

37
Q

Identity lines

A

Reported as pos, makes boomerang shape

38
Q

non-identity lines

A

Negative except in Aspergillus, makes X shape

39
Q

Partial identity line

A

Reported as pos, make Y shape

40
Q

What does a positive line of identity indicate?

A

Indicates that patient antibody was made in response to infection with antigen

41
Q

Who developed the double diffusion 2 dimension system used in fungal serology?

A

Ouchterlony

42
Q

What kind of organism is mycoplasma?

A

It is a member of the Mollicute class. It is free-living (unlike a virus) but does not have a cell wall (unlike a bacteria)

43
Q

What is the incidence of disease caused by Mycoplasma pneumoniae?

A

Leading cause of respiratory infections worldwide. Spread from close contact with infected individuals and has an insidious onset. 5-10% progress to pneumonia. Most common in 5-9 year old’s

44
Q

Why is penicillin not an appropriate therapy?

A

There is no cell wall and penicillin attacks the cell wall

45
Q

What is the principle of the mycoplasma IgM test?

A

Rapid EIA, patient serum is added to wells, 3 drops of conjugate, 3 drops wash buffer and 2 droops substrate. Look for blue color in center after 5 minutes. Test part contains M. pneumoniae antigen and genes as patient test part

46
Q

Alternatives for diagnosing mycoplasma infection

A

Ab detection = complement fixation, ELISA, immunofluorescence, hemagglutination
Culture = no gram stain, dark-field microscopy
Ag detection = PCR

47
Q

What is the importance of an early definitive diagnosis of rotavirus?

A

Isolation, rehydration therapy, no antibiotics

48
Q

What other methods are used to diagnose rotavirus?

A

EIA, membrane EIA, PCR, EM

49
Q

HIV is the etiologic agent of what?

A

AIDS

50
Q

When do HIV patients develop symptoms?

A

3-6 weeks after exposure

51
Q

Asymptomatic period of HIV is characterized by

A

persistent, low level viremia and a gradual depletion of CD4+ T lymphocytes, leading to severe immunodeficiency, multiple opportunistic infections, malignancies and death

52
Q

What is the recommended testing protocol for HIV?

A

HIV 1/2 = Ag/Ab combination assay
HIV 1/2 = ag/Ab differentiation assay
Genotyping
CD4+ counts in flow and HIV quantitative RNA levels to monitor treatment

53
Q

Geenius HIV assay

A

Confirmation test

54
Q

Types of samples for HIV test

A

Serum and EDTA plasma

55
Q

HIV assay detects

A

Antibody

56
Q

What patient populations does the HIV test used for?

A

Adults and pediatric patients with reactive HIV antibody screening results

57
Q

What causes the development of the pink/purple lines in a positive HIV test?

A

Protein-A-colloid gold which binds to captured antibody in sample

58
Q

How can you tell if you performed the HIV test correctly

A

Sample migrates through membrane and a pink/purple line develops in control area that has protein A.

59
Q

How does the operator ensure proper droplet size when adding buffer from the dropper bottle?

A

Hold bottle vertically and freely drop

60
Q

How should the operator handle an “indeterminate” result?

A

Does not exclude the possibility of early seroconversion of the test subject or a cross-reaction with other retroviruses. Should be repeated on new sample in 2-4 weeks

61
Q

Which volatile organic substances are validated from gas chromatograph testing?

A

Isopropanol and Methanol

62
Q

What common household product contains isopropanol?

A

rubbing alcohol

63
Q

What are some consequences of isopropanol ingestion?

A

Increased levels in blood indicate exposure, result in intoxication and CNS depression, can be fatal

64
Q

What products contain methanol?

A

Antifreeze, varnish, shellacs, paints, washer fluid, tobacco, adhesives, homemade distilled spirits

65
Q

What do increased blood levels of methanol indicate?

A

Intoxication, CNS depression, metabolic acidosis

66
Q

Why is only CLRW used for preparing standards?

A

Water with metallic impurities will contaminate or damage the cell

67
Q

Why must samples have their lids crimped prior to preparing the next sample?

A

Prevents evaporation during prep

68
Q

What might happen if the operator turns on the hydrogen without a column connected to the detector fitting inside the oven?

A

H could diffuse into oven and explode. Don’t turn on H until after operator has verified the column is connected to detector

69
Q

What value is considered critical in gas chromatography? What do you do?

A

> 10 mg/dL, must call doctor

70
Q

What are the specimen requirements for the APT test?

A

Stool or gastric fluid with visible blood

71
Q

How to prepare a 0.25 N NaOH solution

A

Dissolve 10 g of NAOH pellets in 1000 mL of CLRW or dilute 2.5 mL of 10 NaOH to 100 mL of CLRW

72
Q

How should the APT specimen look after centrifugation

A

Supernatant should be pink, if not, the test cannot be performed

73
Q

What does a pink result indicate

A

Positive for fetal blood

74
Q

What does a yellow-brown result indicate?

A

Positive for maternal blood

Serology (1 decks)

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