Accuracy of sensitive PSA tests

[Guest guest]

Apropo of the current Question thread and my own experience, I thought it would

be worthwhile to start a discussion about the accuracy of current PSA tests.

Firstly, don't confuse resolution with accuracy. Cheap digital voltmeters often

have two digits of resolution to the right of the decimal place at low voltages.

So if you read 0.05 volt can you expect that the real voltage is 0.05 +/- 0.01?

No, it is probably more like something between 0 and 0.1.

So is the same thing true of PSA tests? I recently received a PSA result from a

new lab of 0.13 whereas the old lab had reported < 0.1 for five years post RP.

Can a lab test have a real accuracy of 0.01 ng/ml when it has to cover a range

from 0.01 to 100 or more? Is a reading of 0.13 accurate within +/-.01 ng/ml. Or

is the PSA test just like the cheap digital voltmeter- it implies a false

accuracy because it has a lot of digits to the right of the decimal point?