BT_PO1.2 Describe the features of a diagnostic test, including the concepts of sensitivity, specificity, positive and negative predictive value and how these are affected by the prevalence of the disease in question.

Don’t forget about this single LO on statistics!

It’s not that difficult to learn this material. I would strongly recommend that you read the two references below. They present the material in a straightforward, and very clinically relevant way.

T/F specificity is the ability of a diagnostic test to detect people who do NOT have a disease

T/F to calculate the sensitivity and specificity of a new diagnostic test, you would apply it to a random sample of the general population

T/F a false negative is a person who HAS the disease, but tested negative on a diagnostic test

T/F to know whether a diagnostic test will be of any clinical value, it is essential to know the prevalence of the disease being tested for

T/F positive predictive value tells us the probability that a given patient HAS the disease if the test is positive

Past SAQ

Make sure you understand this material well enough to answer this past SAQ….

A new test called the “intubation score” has a reported 90% sensitivity and 70% specificity when used to predict difficult intubation. Describe how this information and other statistics related to this test can be used in predicting difficult intubation. How will the incidence of difficult intubation affect the performance of this test? (pass rates have previously been 29-53%)

References

  1. Lalkhen A, McCluskeyA. Clinical tests: specificity and sensitivity. CEACCP 2008; 8: 221-223.
  2. Yentis S. Predicting difficult intubation – worthwhile exercise or pointless ritual? Anaes 2002; 57: 105-109.

Describe the features of a diagnostic test BT_PO 1.2

Why you need to know this is well described in Yentis SM. Predicting difficult intubation – worthwhile exercise or pointless ritual? Anaesthesia 2002 ; 57: 105-109.

In the context of difficult intubation :

TRUE/FALSE  The sensitivity is the proportion of difficult patients who are correctly identified.

TRUE/FALSE  The specificity is the proportion of easy patients who are correctly identified.

TRUE/FALSE  As the prevalence of difficult intubation increases the sensitivity will increase.

TRUE/FALSE  As the prevalence decreases the positive predictive value increases.

TRUE/FALSE  If the test has high specificity it will have a high negative predictive value.