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PSA Standardization



Analytical Difference: Results per 1000 Patients Tested13

Slide 18

October 2009

This was also simulated by Dr. George Klee here at the Mayo Clinic, based on the distribution of 20,000 consecutive patient PSA results that were tested for prostate cancer screening purposes.  Dr. Klee calculated the effect of different levels of analytical bias on the number of results that exceeded the clinical decision level of 4.0 ng/mL.  If there is a positive 6% analytical bias there is an 11% increase in elevated results, and an increased frequency of biopsies.  With a negative 6% analytical bias there is a 14% decrease in detection rate, and the patients would not receive the recommended follow-up testing and/or biopsy.  Similarly, it is clear with a very large bias of 20% the number of patients categorized based on a cutoff greatly increases.  This data suggests that laboratories and manufacturers have to be aware of the great impact of analytical bias in PSA testing and ensure that they reduce this source of error to the lowest possible levels.

Analytical Difference

 


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