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Understanding PSA test numerical results/ decimal places

always concerned
Posts: 1
Joined: Aug 2013

Hi, I hope this information can make it easier to understand the differences in the values when PSA results are reported with one, two or three decimal places. Perhaps it is easier to look at the numbers as if you were buying gasoline.  If we were paying $3.35 for a gallon of gasoline and they added another digit to the right to be "more" accurate and the price was now $3.359...the price is really still $3.35 but very close to becoming $3.36 Thus, the further the digits are from the decimal point, the less meaning they have.

As it relates to PSA scores, a score of 0.1 is the same as 0.10 is the same as 0.100  In this example the zeros after the decimal point are not changing the value. O.1 means one part in ten, 0.10 means 10 parts in 100 and 0.100 means 100 parts in 1000. Its all the same thing.

So, if someone got a PSA score of 0.12 This is 12 parts in 100 or 12/100's. If this same result was reported with three decimal places it would be 0.120 The third value after the decimal is much less significant than the second value after the decimal...and likewise the second value after the decimal is less important than the first number after the decimal. 

A hypothetical ultra sensitive PSA reading reported as 0.025 means there are 25 parts in 1000. If the results were reported as 0.02 there are 2 parts in 100. The third digit could change as follows: 0.025, 0.026, 0.027, 0.028, 0.029  The result (if reported with 2 digits after the decimal place) would still be 0.02 although the third digit lets you see how close you are to the second digit changing. Thus, the next number after 0.029 is 0.030 or 0.03 (same thing)




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