Sensitivity and Specificity

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Education

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• USMLE
• Sensitivity
• and
• specificity

[olhavracsiul]

@rd78565 nice! ;)

[rd78565]

@olhavracsiul Tests that are highly specific are rarely positive when the disease is absent, so when we get a positive result from a specific test we can be confident that it is not a false positive and the patient actually has the disease. If the test is not very specific (like the D-Dimer [Sp=63%]) it generates many false positives. So when we get a positive D-Dimer test we cannot be confident about whether it's a true positive or a false positive. The PVP for the D-Dimer is then very low.

[rd78565]

@olhavracsiul It's important to remember that the D-Dimer test only indicates whether endogenous fibrinolysis is present (and therefore fibrin clots). It's use cannot determine whether or not the clot is a pulmonary embolism, deep venous thrombosis, disseminated intravascular coagulation, or any other particular thrombotic/embolic process. It is also important to distinguish between Sp and Sn and the Positive Predictive Value and Negative Predictive Value.

[mmaris1844]

To remember:

Sensitive: Sn NOUT - a high sensitivity - negative result ruls OUT the diesase

Specificity: Specificity: Sp PIN - a high specificity - positive result ruls IN the disease

[olhavracsiul]

Are you sure about that? according to what you have explained I can say that D-dimer test (used to exclude Pulmonary embolism) is very specific since it excludes correctly a great amount of subjects (a lot of negatives are really negative), and it is little sensitive because it can never tell "this patient has Pulmonary embolism". That's what I thought until reading that it is highly sensitive!

[sergioapuzzo]

thank you



[koropando]

Thanks for sharing ,ur videos r very helpful