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Pulmonology > SM 182 Testing > Flashcards

SM 182 Testing Flashcards

1
Q

Why have vaccines against Strep pneumo and H. flu type B improved outcomes?

A

Vaccines help reduce systemic infections

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2
Q

What type of pathogen tends to cause respiratory infections?

A

Respiratory infections tend to be viral

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3
Q

What is the role of Hemaglutinin in Influenza?

A

HA mediates entry into host cells

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4
Q

What is the role of Neuraminidase in Influenza?

A

NA mediates exit from host cells

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5
Q

What type of virus is RSV and who does it tend to infect?

A

RSV is an RNA virus that tends to cause bronchiolitis and pneumonia in children

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6
Q

Is there a vaccine for RSV?

A

No

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7
Q

What is the prophylactic treatment for RSV?

A

Palvizumab

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8
Q

When and how does RSV spread?

A

RSV is seasonal and spreads via secretions

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9
Q

What type of virus is Adenovirus?

A

Nonenveloped dsDNA virus, found all throughout the body

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10
Q

Why might a positive result for an Adenovirus test be misleading?

A

Adenovirus is found all over the body, and may not actually be responsible for a disease; need a clinical picture to diagnose Adenovirus infection

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11
Q

Why is it hard to test for Adenovirus?

A

There are several serotypes of Adenovirus, which makes it difficult to detect all of them in a single assay

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12
Q

Is adenovirus seasonal?

A

No, Adenovirus and Coronoavirus are year round

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13
Q

Why might NAAT’s not be effective against certain strains of coronavirus?

A

MERS and SARS and nCOV are not detected because they are too new

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14
Q

What are the benefits of tests that rapidly detect respiratory viruses?

A

Reduce antibiotic use, optimize antiviral therapy, infection control and better use of radiographs

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15
Q

When should specimens be collected for analysis and laboratory diagnosis?

A

As early as possible, typically via nasopharyngeal samples

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16
Q

What method cannot be used for clinical diagnosis of a virus?

A

Serology/Antibodies cannot be used to dx a viral infection, ever

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17
Q

What methods can be used for clinical diagnosis of a virus?

A

Molecular methods (ideal), rapid antigen detection, and virus culture

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18
Q

Why is virus culture no longer the gold standard for virus diagnostic testing?

A

Virus culture is no longer recommended because it takes too long to grow the culture

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19
Q

How can viral culture show virus presence?

A

Although culture is no longer used to dx viral infection, the culture could show fusion of the culture cells or be stained with a fluorescent antibody

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20
Q

What are the test characteristics of rapid antigen detection?

A

Fast, but less sensitive than NAAT

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21
Q

What does rapid antigen detection work?

A

RAT detects the antigen-antibody complex

22
Q

What are the pros and cons of RAT?

A

RAT like immunoassays are easy to use, point of care, cheap, and rapid, but have limited sensitivity/assay performance

23
Q

What are the pros of molecular assays?

A

Molecular assays like PCR are fast, high sensitivity, and high specificity

24
Q

How does automation help molecular assays?

A

Allows for simplification of testing process and lowering turnaround time, as well as detection of multiple targets, allowing for detection of multiple targets at the same time

25
Q

Can automated molecular tests detect bacteria or viruses?

A

Automated molecular tests like the FilmArray respiratory panel detect viral and bacterial pathogens simultaneously

26
Q

What are the limitations of multiplex assays?

A

Assay performance (reduced sensitivity for viruses with many serotypes) and increased costs

27
Q

Who are multiplex assays best used on?

A

Seriously infected patients in an inpatient setting that requires intensive care

28
Q

What is a limitation of molecular point of care assays?

A

Although very rapid, these assays are prone to contamination due to operator error

29
Q

Which form of viral detection assay has the lowest sensitivity?

A

Rapid antigen testing via methods like lateral flow have low sensitivity

30
Q

Describe the pathogenesis of TB?

A

Macrophages express TB antigen on MHCII and release IL-12 to activate TB-specific Th1 cells, which in turn release IFN-Gamma to activate Macrophages

31
Q

What two cell types maintain control of TB?

A

Macrophages and Th1 cells

32
Q

What two signaling molecules form a loop that control TB?

A

IL-12 released by Macrophages and IFN-Gamma released by Th1, which allow for granulomatous control of TB

33
Q

Deficiencies in what proteins can result in the loss of control over TB infection?

A

Deficiencies in IL-12 and IFN-Gamma Receptor proteins result in a loss of control over TB as the Granulomatous loop cannot be maintained

34
Q

Repeated mycobacterium infections point to what defect?

A

Defects in IFN-GammaR or IL-12R

35
Q

How can STAT1 phosphorylation be used as a readout of sensitivity to TB infection?

A

After IFN-Gamma binds to its receptor on Macrophages, STAT1 dimerizes and is phosphorylated in B-cells; healthy px show increasing STAT1 phosphorylation with increasing IFN-Gamma, while px with defective IFN-GammaR do not show an increase in STAT1 phosphorylation with increasing IFN-Gamma

36
Q

Is STAT1 loss of function determined by one allele?

A

No; heterozygotes with mutations in 2 loci can result in loss of function of the IFN-GammaR

37
Q

How is the BCG vaccine administered and what can greatly reduce its immunogenic potential?

A

BCG vaccine is administered as a single shot using live attenuated M. bovis, but loses 99% of viability if exposed to the sun

38
Q

What is in the BCG vaccine?

A

Live attenuated M. bovis

39
Q

What are potential complications of the BCG vaccine?

A

Accelerated reactions to the vaccine occur if the px was previously exposed to TB, and infection may disseminate in an immunocompromised host

40
Q

Is the BCG vaccine recommended in the US?

A

No, due to low prevalence of TB < 1%

41
Q

Is the BCG vaccine effective at preventing TB?

A

BCG vaccine can prevent systemic infection of TB, but does not prevent pulmonary disease from TB exposure

42
Q

How does the PPD skin test work?

A

Intradermal administration of non-species specific molecules to induce the formation of a nodule

43
Q

Which species is the PPD skin test using?

A

The PPD skin test is not species specific

44
Q

What can cause a false positive on the PPD?

A

Exposure to NTM like MAC can cause a positive test result on the PPD

45
Q

How is a PPD test read?

A

Measure the diameter of the nodule, not the erythema, and compare to cutoff

46
Q

What are disadvantages tot he PPD skin test?

A

False+ BCG vaccines and repeated testing, false+ with previous NTM exposure, return visit to physicians office required, and inaccuracies with measurement common

47
Q

Does the Quantiferon TB test remove false positives?

A

Uses peptides not found in the BCG vaccine but may still be found in environmental mycobacteria, so removes some but not all false positives

48
Q

How does the Quantiferon TB test work?

A

Uses 4 tubes with 1mL blood; neg control, pos control, and CD4 T cell as well as CD8 T cell responses

49
Q

How does the T-spot test work for TB?

A

Separate PBMC’s from whole blood, and expose peptides not from the BCG (but still may be found in NTM) to cells, and measure spots formed from antibody precipitation = Spot Forming Cells (SFC)

50
Q

What is the gold standard for diagnosing latent TB infection?

A

There isn’t one

51
Q

Can radiology be used to distinguish between active and latent TB?

A

Nope, and neither can the TST or IGRA; need a clinical picture

52
Q

What is one advantage of the Quantiferon over the T-spot?

A

It is unaffected by subjective interpretation of results, like the spot size on the T-spot, and does not require the patient to return to the office

Pulmonology (22 decks)

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