Types of Bias in Studies of Diagnostic Test Accuracy
Received Date: Dec 21, 2015 / Accepted Date: Dec 28, 2015 / Published Date: Jan 04, 2016
The quality of diagnostic accuracy studies assessment is determined by its design, the methods by which the study sample is recruited, the testing involved, blinding in the process of interpreting tests and the study report integrity. Table 1 highlights the main types of bias that can occur in diagnostic accuracy studies [1-8].
|Type of bias||When does it occur?||Impact on accuracy||Preventative measures|
|Patients/Subjects||Selection bias||When eligible patients are not enrolled consecutively or randomly||Usually leads to overestimation of accuracy||Consider all eligible patients and enroll either consecutively or randomly|
|Spectrum bias||When included patients do not represent the intended spectrum of severity for the target condition or alternative conditions||Depends on which end of the disease spectrum the included patients represent||Ensure that the included patients represent a broad sample of those that the test is intended for use within clinical practice|
|Index test||Information bias||When the index results are interpreted with knowledge of the reference test results, or with more (or less) information than in practice||Usually leads to overestimation of accuracy, unless less clinical information is provided than in practice, which may result in an underestimation of accuracy||Index test results should be interpreted without knowledge of the reference test results, or with more (or less) information than in practice|
|Reference test||Misclassification bias||When the reference test does not correctly classify patients with the target condition||Depends on whether both the reference and index test make the same mistakes||Ensure that the reference correctly classifies patients within the target condition|
|Partial verification bias||When a non-random set of patients does not undergo the reference test||Usually leads to overestimation of sensitivity, effect on specificity varies||Ensure that all patients undergo both the reference and index tests|
|Disease/ Condition progression bias Perform the reference and index with minimal delay.||When the patients’ condition changes between administering the index and reference test||Under- or Overestimation of accuracy, depending on the change in the patients’ condition||Ideally at the same time where practical|
|Differential verification bias||When a non-random set of patients is verified with a second or third reference test, especially when this selection depends on the index test result||Usually leads to overestimation of accuracy||Ensure that all patients undergo both the reference and index tests|
|Information bias||When the reference test data is interpreted with the knowledge of the index test results||Usually leads to overestimation of accuracy||Usually leads to overestimation of accuracy|
|Incorporation bias||When the index test is incorporated in a (composite) reference test||Usually leads to overestimation of accuracy||Ensure that the reference and test are performed separately|
|Data analysis||Excluded data||When uninterruptable or intermediate test results and withdrawals are not included in the analysis||Usually leads to overestimation of accuracy||Ensure that all patients who entered the study are accounted for and that all uninterruptable or intermediate test results are explained|
Was a consecutive or random sample of patients enrolled?
Was a case-control design avoided?
Did the study avoid inappropriate exclusions?
Were the index test results interpreted without knowledge of the results of the reference standard?
If a threshold was used, was it pre-specified?
Is the reference standard likely to correctly classify the target condition?
Were the reference standard results interpreted without knowledge of the results of the index test?
Flow and timing
Was there an appropriate interval between the index test and reference standard?
Did all patients receive the same reference standard?
Were all patients included in the analysis?
Table 1: Understanding this bias can improve the design and evaluation of diagnostic accuracy studies.
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Citation: Roever L (2016) Types of Bias in Studies of Diagnostic Test Accuracy. Evidence Based Medicine and Practice 1: e113. Doi: 10.4172/2471-9919.1000e113
Copyright: © 2016 Roever L. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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