Advanced Field Epi:Manual 2 - Diagnostic Tests/en - Revision history

FuzzyBot: Importing a new version from external source

2015-05-10T07:50:37Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:50:20Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:50:19Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:50:13Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:48:51Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:48:37Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:48:09Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:44:44Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:44:40Z

Importing a new version from external source

FuzzyBot: Importing a new version from external source

2015-05-10T07:44:39Z

Importing a new version from external source

@@ Baris 195: / Baris 195: @@
 Two or more tests can be used either sequentially or simultaneously and results interpreted in series or parallel. In parallel interpretation, an animal is considered positive if it reacts positively to either or both tests - this increases sensitivity but tends to decrease the specificity of the combined tests. In series interpretation, an animal must be positive on both tests to be considered positive - this increases specificity at the expense of sensitivity.
-'''''Parallel''' interpretation of tests means that both tests must give a positive result for the animal to be considered positive. Parallel testing increases sensitivity but tends to decrease the specificity, compared to using either test in isolation.''
+{{hlbox|'''''Parallel''' interpretation of tests means that both tests must give a positive result for the animal to be considered positive. Parallel testing increases sensitivity but tends to decrease the specificity, compared to using either test in isolation.''
 '''''Series''' interpretation of tests means that the animal is considered positive if either of the tests gives a positive result. Series testing increases specificity at the expense of sensitivity, compared to using either test in isolation.''}}

@@ Baris 682: / Baris 682: @@
 ==== Maximum likelihood estimation  ====
-Maximum likelihood methods use standard statistical methods to estimate sensitivity and specificity of multiple tests from a comparison of the results of multiple tests applied to the same individuals in multiple populations with different prevalence levels ([#_ENREF_9 Hui and Walter, 1980]<nowiki>; </nowiki>[#_ENREF_4 EnÃ¸e et al., 2000]<nowiki>; </nowiki>[#_ENREF_15 Pouillot et al., 2002]). Key assumptions for this approach are:
+Maximum likelihood methods use standard statistical methods to estimate sensitivity and specificity of multiple tests from a comparison of the results of multiple tests applied to the same individuals in multiple populations with different prevalence levels ([#9 Hui and Walter, 1980]; [#4 EnÃ¸e et al., 2000]; [#15 Pouillot et al., 2002]). Key assumptions for this approach are:
 * The tests are independent, conditional on disease status (the sensitivity [specificity] of one test is the same, regardless of the result of the other test, as discussed in more detail in the section on series and parallel interpretation of tests);

@@ Baris 677: / Baris 677: @@
 {{hlbox|'''''Non gold-standard '''test evaluation makes no explicit assumptions about the disease state of the animals tested and relies on statistical methods to determine the most likely values for test sensitivity and/or specificity''}}
-Although these methods donâ€™t rely on a gold standard for comparison, they do depend on a number of important assumptions. Violation of these assumptions could render the resulting estimates invalid. Non-gold-standard methods for estimating sensitivity and specificity of diagnostic tests have been described in more detail by Hui and Walter ([#_ENREF_9 1980]), Staquet et al. ([#_ENREF_19 1981]) and EnÃ¸e et al. ([#_ENREF_4 2000]).
+Although these methods don't rely on a gold standard for comparison, they do depend on a number of important assumptions. Violation of these assumptions could render the resulting estimates invalid. Non-gold-standard methods for estimating sensitivity and specificity of diagnostic tests have been described in more detail by Hui and Walter ([#9 1980]), Staquet et al. ([#19 1981]) and Enøe et al. ([#4 2000]).
 Available non-gold-standard methods include:

@@ Baris 127: / Baris 127: @@
 '''''Sensitivity''' (True Positive Fraction): The proportion of animals with the disease of interest that test positive. Sensitivity is also defined as the conditional probability that a test will correctly identify those animals that are infected (Pr T+|D+).''
-The ''false negative fraction'' is 1 â€“ Se.
+The ''false negative fraction'' is 1 - Se.
 === Specificity ===

@@ Baris 660: / Baris 660: @@
 If a disease is rare, or if the "gold standard" test is complex and expensive to perform, sample sizes for estimation of sensitivity are likely to be small, leading to imprecise estimates of sensitivity. If a disease does not occur in a country it is impossible to estimate sensitivity in a sample that is representative of the population in which it is to be applied. Conversely, if a disease does not occur in a country or region, it is relatively easy to estimate test specificity, based on a representative sample of animals from the population, because if the population is free of disease all animals in the population must also be disease-free.
-Sometimes a new test may appear to be more sensitive (or specific) than the existing â€œgold standardâ€ test (for example, new DNA-based tests compared to conventional culture). In this situation, the new test will find more (or fewer) positives than the reference test and careful analysis is required to determine whether this is because it is more sensitive or less specific. Even then, it is often not possible to reliably estimate sensitivity or specificity because there is no fixed reference point, so it may only be possible to say that the new test is more sensitive (or specific) than the old test, without specifying a value.
+Sometimes a new test may appear to be more sensitive (or specific) than the existing "gold standard" test (for example, new DNA-based tests compared to conventional culture). In this situation, the new test will find more (or fewer) positives than the reference test and careful analysis is required to determine whether this is because it is more sensitive or less specific. Even then, it is often not possible to reliably estimate sensitivity or specificity because there is no fixed reference point, so it may only be possible to say that the new test is more sensitive (or specific) than the old test, without specifying a value.
 Gold-standard methods for estimating sensitivity and specificity of diagnostic tests and their limitations are discussed in more detail by Greiner and Gardner ([#8 2000]).

← Revisi sebelumnya		Revisi per 10 Mei 2015 07.48
Baris 662:		Baris 662:
	Sometimes a new test may appear to be more sensitive (or specific) than the existing â€œgold standardâ€ test (for example, new DNA-based tests compared to conventional culture). In this situation, the new test will find more (or fewer) positives than the reference test and careful analysis is required to determine whether this is because it is more sensitive or less specific. Even then, it is often not possible to reliably estimate sensitivity or specificity because there is no fixed reference point, so it may only be possible to say that the new test is more sensitive (or specific) than the old test, without specifying a value.		Sometimes a new test may appear to be more sensitive (or specific) than the existing â€œgold standardâ€ test (for example, new DNA-based tests compared to conventional culture). In this situation, the new test will find more (or fewer) positives than the reference test and careful analysis is required to determine whether this is because it is more sensitive or less specific. Even then, it is often not possible to reliably estimate sensitivity or specificity because there is no fixed reference point, so it may only be possible to say that the new test is more sensitive (or specific) than the old test, without specifying a value.

−	Gold-standard methods for estimating sensitivity and specificity of diagnostic tests and their limitations are discussed in more detail by Greiner and Gardner ([#~~_ENREF_8~~ 2000]).	+	Gold-standard methods for estimating sensitivity and specificity of diagnostic tests and their limitations are discussed in more detail by Greiner and Gardner ([#8 2000]).

@@ Baris 156: / Baris 156: @@
 Se and Sp are characteristics of the test when the test is applied to animals of known disease status. Se and Sp do not tell us how useful the test might be when applied to animals of unknown disease status.
-For most people in the field, the practical situation is that they have performed the test on an animal with unknown disease status and they wish to use the test results to better classify the animal as disease + or disease -. Se and Sp are not helpful in this situation.
+For most people in the field, the practical situation is that they have performed the test on an animal with unknown disease status and they wish to use the test results to better classify the animal as disease + or disease - Se and Sp are not helpful in this situation.
 Predictive values are useful in this situation. Predictive values allow us to answer the two related questions:

@@ Baris 695: / Baris 695: @@
 ==== Comparison with a known reference test ====
-Sensitivity and specificity can also be estimated by comparison with a reference test of known sensitivity and/or specificity ([#_ENREF_19 Staquet et al., 1981]). These methods cover a variety of circumstances, depending on whether sensitivity or specificity or both are known for the reference test. Key assumptions are conditional independence of tests, and that the sensitivity and/or specificity of the reference test is known.
+Sensitivity and specificity can also be estimated by comparison with a reference test of known sensitivity and/or specificity ([#19 Staquet et al., 1981]). These methods cover a variety of circumstances, depending on whether sensitivity or specificity or both are known for the reference test. Key assumptions are conditional independence of tests, and that the sensitivity and/or specificity of the reference test is known.
 In the special situation where the reference test is known to be close to 100% specific (for example culture or PCR-based tests), the sensitivity of the new test can be estimated in those animals that test positive to the reference test:

@@ Baris 220: / Baris 220: @@
 Sp<sub>parallel</sub> = Sp<sub>1</sub> ï‚´ Sp<sub>2</sub> = 0.973 or 97.3% for this example and
-Sp<sub>series</sub> = 1 â€“ (1 â€“ Sp<sub>1</sub>) ï‚´ (1 â€“ Sp<sub>2</sub>) = 0.999 or 99.9% for our example
+Sp<sub>series</sub> = 1 - (1 - Sp<sub>1</sub>) ï‚´ (1 - Sp<sub>2</sub>) = 0.999 or 99.9% for our example
 [[Image:Scenario tree 1.jpg]]

@@ Baris 393: / Baris 393: @@
 |-
-| style="border:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| <center>>0.2 â€“ 0.4</center>
+| style="border:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| >0.2 - 0.4
 | style="border:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.191cm;padding-right:0.191cm;"| Fair agreement