Serial and Parallel Testing Flashcards
Serial testing
2 or more tests are conducted sequentially based on the results of a previous test
Only animals that test ______ to the first test are tested again
Positive!!
Only animals that are ______ on all tests are considered ______
Positive; positive!!
When is serial testing used?
Used for diagnosis when time is not crucial
- or if diagnosing a patient when disease positive has grave outcome
With serial testing, is test 2 different than test 1?
Yes!
- if both tests are positive, then the animal is classified as sick
What is the probability of properly identifying a truly sick patient through the testing program (2 tests)
Is the overall (combined) sensitivity
Parallel testing
Conducting 2 or more tests on a patient at the same time
With parallel tests, a patient is considered positive if ______
They are positive to any of the tests
- if any one test is positive they are classified as sick
If serial testing has low sensitivity and high specificity, then parallel testing has ______
High sensitivity, low specificity
When is parallel testing used?
For rapid assessment of individual patients in emergencies
- not used often in vet med
The only way an animal is classified as not sick in parallel testing is if ______
Both tests are negative!
- animal has to prove it does not have disease
In serial testing, you make the animal prove ________
That it has the disease
What are the chances an animal is test negative on both tests? (parallel)
Probability to be negative on both tests for those not sick = proportion negative on test 1 x proportion negative on test 2
Probability to be negative on both tests
Specificity test 1 x specificity test 2
Probability of sick to be negative on both tests (parallel)
False negative probability test 1 x false negative probability test 2
Overall increased sensitivity =
Fewer false negatives
Decreased specificity =
More false positives
Parallel testing is used when the consequence of missing a disease has _____ importance than having false positives
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)
Parallel testing has overall increased _______
Sensitivity!
With serial testing you miss ______
Many ill animals
- decreased sensitivity
- increased specificity = those who are well are likely to test negative
Serial testing is used when the consequence of a ______ is more important than missing a diseased animal
False positive
- useful in disease eradication programs in which positive animals are culled from the herd
Serial testing increases overall _______
Specificity
- decreases overall sensitivity, allowing more diseased animals to remain in the herd
Serial testing - summary
- 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
Values of serial testing will vary depending on ______
- sensitivity
- specificity
- prevalence
Parallel testing - summary
- 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!
Parallel testing values will vary depending on _______
- sensitivity
- specificity
- prevalence
