Actual Epi Flashcards by Mary Ellen Josephine Mangiameli

Use of diagnostic tests in clinical medicine is for ?

Treatment and prognosis

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Describe a very sensitive test

Many true positive test results

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Use of diagnostic tests in surveillance are for ?

Identifying changes in dz status in a POPULATION

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Describe a very specific test

Many true negative test results

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Use of diagnostic tests in international trade are for ?

Keeping infected animals OUT

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Use of diagnostic tests in research are for?

Identifying and monitoring research subjects

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When do we want to use a highly sensitive test?

When we need to detect ALL diseased/infected animals

I.e. Testing imported animals

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When do we want to use a highly specific test?

When the cost of a FALSE positive (ie.e needing to cull all positive animals)

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If there are a lot of false negatives, what property does the test have?

Low SENSitivity

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If there are a lot of false positives, what property does the test have?

low SPECificity

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What is the “incidence” of death in a given time? (type of rate)

Mortality rate

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What do we call the number of cases in a population that died after exposure to a disease (type of rate)?

Case fatality rate

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In a cross sectional study, what is the measure of disease exposure?

Prevalence/odds

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In a case control study, what is the measure of disease exposure?

Odds

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In a prospective cohort study, what is the measure of disease exposure?

Incidence

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In a retrospective cohort study, what is the measure of disease exposure?

Prevalence

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In a clinical trial study, what is the measure of disease exposure?

Incidence

When do we use relative risk as a measure of association?

Prospective cohort and clinical trials

If there is no vaccine history or if the patient is WAY overdue for their rabies vaccination, and has been exposed to the disease, what is our protocol?

Euthanize immediately.

IF the owner is unwilling,

1) manage the bite wounds
2) strict quarantine for 4 months and observe for neuro signs
3) vaccinate within 96 hours of exposure

If a patient is current on all vaccinations, and has been exposed to Rabies, what is our protocol?

1) manage bite wounds
2) home confinement for 45 days and observe for neuro signs
3) revaccinate immediately

If a patient is overdue for his/her Rabies booster, and has been exposed to the disease, what is our protocol?

WITH documentation: delayed within months (NOT years); treat as if they are current on their vax

WITHOUT documentation: treat as if they are not vaccinated or serological monitoring

What is R0 (“R-naught”)?

The basic reproductive number of an infection in a population

In regards to surveillance, how can emerging diseases be identified?

Referral labs with the help of DVMs

If the reproductive rate of a new disease virus is R0 (R “naught”)=10, what percentage of the human population needs to be vaccinated to prevent a great spread?

Vc=1-(1/R0)
Vc=1-(1/10)
Vc=1-(0.1)
Vc=0.9

So 90% needs to be vaccinated!

We see a stray kitten and the new owner has been scratched and bitten. Physical exam was WNL; what is the protocol?

Observe for the next 10 days for neuro signs; DO NOT vaccinate against rabies until the end of the observation period

Leptospira in cattle study: purpose was to estimate the seroprevalence of Lepto Abs in cattle on the Andaman Islands. A total of 494 serum samples were collected from a random sample of cattle on the islands. Abs to Lepto were detected in 164 samples, giving an overall seroprevalence of 33.11%. What is the study design?

Descriptive cross-sectional

PCR is an example of what type of diagnostic test?

Continuous

Physical exam, post-mortem, and diagnostic imaging are examples of what type of diagnostic test?

Dichotomous

``` An outbreak of Cryptosporidiosis in vet students study. GI illness due toe C.parvum occurred in a class of 96 students in a NZ vet school. At the end of the first week of the outbreak, 25/80 (31%) of students interviewed HAD the GI dz. the source of infection could not be definitively identified, but the investigation suggested contact with calves during a practical class as the most likely cause. ``` What is the type of measure? What type of incidence? How many students were in the study population vs the source population?

RATE; Cumulative incidence; Study pop: 80 Source pop: 96

Porcine Parvovirus Abs in sows from swine herds of Bahia, Brazil. Study of infection in swine farms included 221 lactating sows that were randomly selected from 11 randomly selected farms in the state. Blood samples were taken from each sow to determine the levels of Abs against the dz in the herds by the hemagglutination inhibition test. Results showed 94.12% (208/221) of the sows had protective HI titers. What is this an example of? What type of measurement is this?

Point prevalence | Proportion

Schmallenburg in the Netherlands study. This report describes the clinical signs and pathology seen in the first 6 cases of the virus infection in lambs in the Netherlands. Since December 2011, the Netherlands Animal Health Service received reports of the birth of deformed lambs born with defects such as torticollis and arthrogryposis. Some deformed lambs were born dead. In some lambs, brain abnormalities were observed such as hydranencephaly or hypoplasia. What is the study design?

Case SERIES

What is a disadvantage of ecological studies?

Ecological fallacy

What do case-control studies determine?

Prevalence only!

Between retrospective and prospective studies, which has a shorter timeline?

Retrospective

Between retrospective and prospective studies, which establishes causality better?

Prospective!

Between retrospective and prospective studies, which has to deal with changing populations?

Prospective

P-values. When p-value is less than _____, it is statistically significant and thus we can _______ the null hypothesis.

0.05; reject

The smaller the p-value, the ______ the association.

Stronger!

Regarding 95% confidence intervals, the width of the CI is related to what?

Sample size

Regarding 95% confidence intervals, small sample sizes have larger or smaller CIs?

LARGER

The prevalence of heartworm in the area is 10%. What is the positive predictive value of the test (PPV)? A SLAP heartworm Ag test with a reported sensitivity of 96% and specificity of 98% is being used.

84.2%