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What are sensitivity and specificity?
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  • Published on: 24 May 2021
    Figure 3?

    Am I muddled? Figure 3 is labelled as an example of 'high specificity'. Just following the simple rules set out for figure 2 shows that: specificity = number of true negatives / (true negatives + false positives) = 8/ (8 + 62) = 0.1111 or 11% & sensitivity = number of true positives (true positives + false negatives) = 30 (30 + 0) = 1 or 100%. Surely this is a highly sensitive test??

    Comment from the Editor: Thanks to Dr. McDermott for these comments, please see the corrected version of the paper at https://ebn.bmj.com/content/25/2/e1 We hope it addresses all your concerns.

    Conflict of Interest:
    None declared.
  • Published on: 6 May 2021
    Re: Swift A, Heale R, Twycross A. What are sensitivity and specificity? Evidence-Based Nursing 2020;23:2-4.
    • Anthony Codd, GP Academic Clinical Fellow Newcastle University

    I read this article with interest as I revised for an recent assessment. I have some comments which may be of use to you and your readers, as I feel there are mistakes in the use of the terms sensitivity and specificity, which seem to be interchanged at various points throughout the article, and notably in the second paragraph, where there are initially defined. From my understanding, the ability of a test to correctly identify a disease is sensitivity, and the ability to correctly identify the absence of a disease is specificity, rather than he reverse as presented here. This may be typographical, as the authors go on to correctly illustrate both sensitivity and specificity in the subsequent example, and in Box 1, however further instances of this error appear later.

    Another prominent example is Fig 3 and the associated paragraph, which I believe refers to high sensitivity, rather than specificity. As specificity is TN/(TN+FP), a higher false positive rate would decrease specificity. The figure shows a test which is highly sensitive ((TP/(TP+FN) = 30/(30+0) = 1 = 100%), but with low specificity ((TN/(TN+FP) = 8/(8+62) = 8/70 = 0.11 = 11%).

    There seems to be a further confusion, particularly in the paragraph using the Ottawa ankle rule as an illustrative example. The 'wide range of sensitivity' discussed early in this paragraph, is not sensitivity, but specificity as stated in the discussion of the cited article (8). Indeed, this is indicated in t...

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    Conflict of Interest:
    None declared.
  • Published on: 25 February 2021
    Error in Figure 3

    I may have missed something but the Figure 3 does not illustrate high specificity, it shows perfect sensitivity and very low specificity. There is the same confusion in the paragraph that explains it "There is a risk that a test with high specificity will capture some people who do not have Disease D (figure 3). The screening test in figure 2 will capture all those who have the disease but also many who do not. " That would be a test with high sensitivity. And the reference to the figures is confusing (I believe the authors are referring to Figure 3 all along).

    "Comment from the Editor: Thanks to Dr. Lassale for these comments, please see the corrected version of the paper at https://ebn.bmj.com/content/25/2/e1"

    Conflict of Interest:
    None declared.
  • Published on: 12 January 2021
    Multiple Corrections

    I am writing to highlight what I believe to be several fundamental errors in this article in trying to explain sensitivity and specificity, titled “What are sensitivity and specificity?”

    http://dx.doi.org/10.1136/ebnurs-2019-103225

    1) Partway through, the article states, "there is a risk that a test with high specificity will capture some people who do not have Disease D (figure 3)."

    I believe this should state "high sensitivity", not high specificity, as this would be the complete opposite with low false positives. The same applies for the "high specificity" label for Figure 3 - this illustrates a high sensitivity test (with very low specificity as it gives many false positives), not a high specificity test.

    2) In reference to the Ottawa ankle rules:
    "They have been shown (in a systematic review) to correctly identify approximately 96% of people who have a fracture and to correctly rule out between 10% and 70% of those who do not have a fracture.(8) The wide range of sensitivity is likely to be due to differences in the education of the clinicians involved".
    Assuming a positive test here identifies ankle fractures, I believe this is a wide range in 'specificity', not a "wide range of sensitivity" (which appears to be c.96%).

    Sensitivity and specificity are repeatedly swapped incorrectly in this sect...

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    Conflict of Interest:
    None declared.
  • Published on: 14 November 2020
    sensitivity vs specificity

    I think these have been confused in the "definitions"

    "Comment from the Editor: Thanks to Dr. Nicholl for these comments, please see the corrected version of the paper at https://ebn.bmj.com/content/25/2/e1"

    Conflict of Interest:
    None declared.