Serial and Parallel Testing

Question 1

Serial testing

Answer 1

2 or more tests are conducted sequentially based on the results of a previous test

Question 2

Only animals that test ______ to the first test are tested again

Answer 2

Positive!!

Question 3

Only animals that are ______ on all tests are considered ______

Answer 3

Positive; positive!!

Question 4

When is serial testing used?

Answer 4

Used for diagnosis when time is not crucial

- or if diagnosing a patient when disease positive has grave outcome

Question 5

With serial testing, is test 2 different than test 1?

Answer 5

Yes!

- if both tests are positive, then the animal is classified as sick

Question 6

What is the probability of properly identifying a truly sick patient through the testing program (2 tests)

Answer 6

Is the overall (combined) sensitivity

Question 7

Parallel testing

Answer 7

Conducting 2 or more tests on a patient at the same time

Question 8

With parallel tests, a patient is considered positive if ______

Answer 8

They are positive to any of the tests

- if any one test is positive they are classified as sick

Question 9

If serial testing has low sensitivity and high specificity, then parallel testing has ______

Answer 9

High sensitivity, low specificity

Question 10

When is parallel testing used?

Answer 10

For rapid assessment of individual patients in emergencies

- not used often in vet med

Question 11

The only way an animal is classified as not sick in parallel testing is if ______

Answer 11

Both tests are negative!

- animal has to prove it does not have disease

Question 12

In serial testing, you make the animal prove ________

Answer 12

That it has the disease

Question 13

What are the chances an animal is test negative on both tests? (parallel)

Answer 13

Probability to be negative on both tests for those not sick = proportion negative on test 1 x proportion negative on test 2

Question 14

Probability to be negative on both tests

Answer 14

Specificity test 1 x specificity test 2

Question 15

Probability of sick to be negative on both tests (parallel)

Answer 15

False negative probability test 1 x false negative probability test 2

Question 16

Overall increased sensitivity =

Answer 16

Fewer false negatives

Question 17

Decreased specificity =

Answer 17

More false positives

Question 18

Parallel testing is used when the consequence of missing a disease has _____ importance than having false positives

Answer 18

Greater
- used to rule out disease or when no one test is very sensitive or when 2 tests detect different stages of disease (acute and chronic)

Question 19

Parallel testing has overall increased _______

Answer 19

Sensitivity!

Question 20

With serial testing you miss ______

Answer 20

Many ill animals

• decreased sensitivity
• increased specificity = those who are well are likely to test negative

Question 21

Serial testing is used when the consequence of a ______ is more important than missing a diseased animal

Answer 21

False positive

- useful in disease eradication programs in which positive animals are culled from the herd

Question 22

Serial testing increases overall _______

Answer 22

Specificity

- decreases overall sensitivity, allowing more diseased animals to remain in the herd

Question 23

Serial testing - summary

Answer 23

• overall sensitivity: low
• overall specificity: high
• confidence in + test: high (high PPV)
• confidence in negative test: low (lower NPV)
• relatively small number of + tests, pool of + tests is nearly all sick but not all sick are in the test + pool
• • test identifies animal and high probability of illness, rules in disease with confidence in positives

Question 24

Values of serial testing will vary depending on ______

Answer 24

• sensitivity
• specificity
• prevalence

Question 25

Parallel testing - summary

Answer 25

• overall sensitivity: high
• overall specificity: low
• confidence in + test: lower (lower PPV)
• confidence in neg test: high (higher NPV)
• more + tests, + pool captures almost all ill, but includes many non-ill too
• neg test pool identifies well animals, rules out disease, so confidence in negatives!

Question 26

Parallel testing values will vary depending on _______

Answer 26

• sensitivity
• specificity
• prevalence