So Yeppoon it was ...

Early rise and off inland to Biloela.   First thing I noticed even as I was leaving Gladstone was that things were a lot drier than in February.  Less green.  Weird approaching winter but up here its coming up to dry season.  The drive into Biloela and then north to Mt Morgan was a long, but interesting drive through inland country, much of it farming land.  Mt Morgan is a town at the peak of a mountain range, quite a nice place.  Apparently it can get really cold there.

 

Then through Rockhampton and to Yeppoon and around to Keppell Bay.  I ended up chosing not to go across to Keppell Island or do a coral cruise.  Just seemed a wierd thing to do by myself, so I wandered along the beach at Yeppoon and around the marina and exotic and no doubt outrageously expensive marina-side units.

 

The first photo is from Yeppoon looking towards Keppell Bay and the other is east out to the reef from the beach near the marina.

 

You can leave now .. just going to talk a about pathology testing.

 

If you are still reading you might want to pop over here to check out the terms specificity and sensitivity.

 

http://en.wikipedia.org/wiki/Sensitivity_and_specificity

 

If one designs the perfect test it is going to give 100% accuracy on determining those with the disease state being tested.  No one with the disease comes up with a "negative test", the false negative, and no one without the disease comes up with a "positive test" - the false positive.

 

I know of no such perfect test.  Some tests are to diagnose the presence of a disease and some tests are to exclude (if one can) the presence of a disease.

 

The "good" exclusion tests are used for screening, eg, faecal occult blood tests for bowel cancer.  See the wiki example for a detailed explanation.

 

Some tests are not good .. but still used.  Why are they not good ?   Because of the high rate of false positives.  And why is this not good ?  Not only is this not good for the mental health of the patient without the disease but an abnormal result but can lead to potentially invasive and harmful investigation to exclude the disease that the first test with its false positive failed to exclude.

 

Why do we do these tests ?   I have a suspicion it is related to lack of clinical confidence and fear of mistakes and subsequent litigation.

 

So who then is to blame for the persistent use of tests that a positive result is more than 50% likely to be a false positive even ... and is the cost of the false positive worth the use of the test simply because it rarely gives a false negative and therefore a negative test result can be reassuring ? .. you try to answer that one if you can.

 

Back again sometime soon.