Lab assays

Question 1

accuracy vs precision?

Answer 1

accurate tests get close on average to the right answer, precise tests have consistently reproducible results (may not necessarily be “correct” though)

Question 2

Which test property most influences test performance with…low organism burden?

Answer 2

sensitivity

Question 3

Which test property most influences test performance with…potential detection of closely related organisms?

Answer 3

specificity

Question 4

Which test property most influences test performance with…too little specimen?

Answer 4

sensitivity

Question 5

Which test property most influences test performance with…low prevalence population?

Answer 5

specificity

Question 6

Pros/cons of microscopy?

Answer 6

Pros: low cost, rapid results
Cons: what you see is what you get

Question 7

Culture pros/cons?

Answer 7

Pros: recovery of live organisms, higher specificity than microscopy
Cons: requires specialized media, incubator etc, lower specificity than NAATs, and some bugs can’t be cultivated in vivo

Question 8

Viral culture issues?

Answer 8

requires host cells, $$$, special labor, equipment, and training

Question 9

How does a blood culture work?

Answer 9

1. blood drawn and split into 2 bottles (1 set)
2. 2 sets overall taken from 2 different body sites to confirm there is no contamination
3. when results from both sets are the same, source is organism in patient’s blood

Question 10

How are antibody detection tests/serology retrospective?

Answer 10

Because we form antibodies in response to infection. If you’re detecting antibodies to a certain organism/pathogen, that infection happened in the past.

Question 11

Antigen detection tests look for what?

Answer 11

the presence of the organism in the specimen

Question 12

Direct fluorescence microscopy assays are an example of what kind of testing?

Answer 12

antigen detection test

Question 13

Rapid stress tests fall under what category of testing?

Answer 13

antigen detection test

Question 14

Particle agglutination tests fall under what category of testing?

Answer 14

antigen detection test

Question 15

Explain how NAATs work.

Answer 15

enzymatically amplify target viral DNA/RNA molecules (i.e. by PCR, rtPCR, or other techniques)

Question 16

Pros of NAATs?

Answer 16

highly sensitive (compared to microscopy, cultures, or antigen detection) and more specific for nucleotide sequences, doesn’t require live organisms

Question 17

Exponential amplification refers to?

Answer 17

millions of copies of a template molecule that can be amplified quickly using NAATs

Question 18

Potential shortfall of NAATs?

Answer 18

high sensitivity can pick up dead organisms - may lead you to believe there’s an ongoing infection when abx have actually killed organisms

Question 19

Explain how NAATs can lead to less invasive testing

Answer 19

Example of STDs - sensitivity of NAATs is so high that you can take use a urine sample instead of an invasive/uncomfortable endocervical or urethral swab

Question 20

Set up needed for antimicrobial susceptibility tests?

Answer 20

in vitro test with live organisms grown in presence of antimicrobial agents; may find genetic basis of resistance