The ‘Snout’ and ‘Spin’ rule – Explained

Sensitivity

If a person has an injury, this measures how sensitive is the test to detect/pick up the problem

So if a test has a high sensitivity, you can be confident it will detect the injury… and so if the test result is negative… you can be nearly certain that they don’t have disease. 

A Sensitive test helps rule out injury (when the result is negative).

So we say: Sensitivity rules out or “Snout”

Specificity

High specificity tests are very specific with what they screen for. While a highly sensitive test will say ‘We have a problem’, your highly specific test can reliably say ‘Its not the problem we are screening for’. In other words its very good at excluding.

So if the test has a high specificity and the result is positive… you can be near certain that they do have the injury you screened for (as they have passed the ‘exclusion test’).

A very specific test helps rule in an injury with a high degree of confidence.

So we say: Specificity rule in or “Spin”

SUMMARY:

  • High sensitivity + negative result = Strong indication!
  • High specificity + positive result = Strong indication!

IMAGE:
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