Hi Alex!
A confusing topic for sure! Using SPIN and SNOUT when talking about sensitivity and specificity can cause some confusion at times. Often people use the mnemonics SPIN and SNOUT as definitions of specificity and sensitivity, but they and not the definitions. They are mnemonics to remember the RELATIONSHIP of sensitivity and specificity for ruling in and ruling out a diagnosis based on a TEST result.
Sensitivity (true positive rate) is the likelihood that someone with the condition will be positive on the diagnostic test and refers to the percentage of children who are correctly identified as meeting criteria for a condition. This is valuable for confirming a diagnosis and 80% sensitivity is preferable.
Specificity (true negative rate) is the likelihood that someone who does not have the condition will be negative on the diagnostic test and refers to the percentage of children without problems who are correctly identified as such. This is valuable to rule out the presence of a condition and 90% is preferable.
Does this help clear up the confusion?