Epidemiology

Front 1

What is the definition of predictive values?

Back 1

quantify the probability that a test result for a particular animal correctly identifies th econdition of interest; takes into account test characterisitcs during the diagnostic decision process

Front 2

Predictive value positive test?

Back 2

stands for the proportion of test postitive animals which really have the disease

Front 3

Predictive value negative test?

Back 3

proportion of test negative which really do not have disease

Front 4

Estimation of predictive values requires what three values?

Back 4

sensitivity, specificity, and the prevalence of hte condition in a population

Front 5

True or False:
sensitivity and specificity are independent of prevalence?

Back 5

True

Front 6

True or False:
If prevalence increases, positive predictive value decreases and negative predictive value decreases?

Back 6

False: positive predictive value increases

Front 7

Ture or False:
If prevalence decreases, positive predictive value decreases and negative predictive value decreases

Back 7

False: negative predictive value increases

Front 8

True or False:
The more sensitive the test, the better the negative predictive value.

Back 8

True

Front 9

True or False:
The more specific at test, the better is the positive predictive value.

Back 9

True

Front 10

What is the definition of the apparent prevalence?

Back 10

the proportion of all animals that give a positive test result

Front 11

How can estimates of true prevalance be made?

Back 11

can be obtained by taking account of test sensitivity and specificity using the formula

true prevalence= (apparent prevalence = (specificity -1))/ (specificity + 1 (sensitivity -1))

Front 12

What is the calculation for sensitivty?

Back 12

a/ (a+c)

Front 13

What is the calculation for specificity?

Back 13

d/ (b+d)

Front 14

What is the calculation for the negative predictive value?

Back 14

d/ (c+d)

Front 15

What is the calculation for the positive predictive value?

Back 15

a/ ( a+b)

Front 16

What is the calculation for apparent prevalence?

Back 16

(a+b)/N

Front 17

What is the calculation for true prevalence?

Back 17

(a+c)/N

Front 18

What are some differnt sampling methods?

Back 18

homogenous: simple random
definite strata, each straum has proportionate ratio of number of members of other strata: simple stratified
definite strata, each stratum has proportionate ratio of number of members of other strata: proportional stratified
groups with similar characteristics but heterogeneous within group: cluster
No sampling frame for units of interest: multistage

Front 19

What is causation?

Back 19

It is cause effect relationship
following criteria are needed to be considered the cause of a disease:
present in every case, isolated and grwon in pure culture, has to cause a specific disease and then be recovered (these were the 1st characteristics known as Koch's postulates)

Front 20

What is the epidemiological triad?

Back 20

agent, host, and environment all lead to a part in the disease (forms the triangle with disease in the middle)

Front 21

What is the cummulative incidence (incidence risk)?

Back 21

risk of new disease occurence; proportion of disease-free individuals developing a given disease over a specified time, conditional on that individual's not dying from any other disease during the period, individual risk of contacting the disease in a period of time

Front 22

What is incidence density?

Back 22

defined as the instantaneous potential for change in disease status per unit of time at time t, relative to the size of the disease free population at time t; the enumerator is the number of new cases over the period observed and the denominator is the accumulated sum of all individuals time at risk

Front 23

What is prevalence?

Back 23

Proportion of a population affected by a disease @ a given point in time. Probabliltyof an individual from the same population having the disease at this point in time.