Arecent nationwide study investigated the value of the prostate-specific antigen (psa) blood test for the detection of prostate cancer among 100,000 men 50 years of age and older. of the 686 men who tested positive on the psa test, a total of 281 were ultimately diagnosed with prostate cancer, either by immediate needle biopsy or during 12 months of watchful waiting. an additional 45 men who tested negative on the psa test were ultimately diagnosed with prostate cancer during 12 months of follow-up. a screening test is available to identify individuals with a genetic mutation that puts them at greater risk for stroke. the test is extremely expensive and is not covered by most insurance plans, so those choosing to have the test usually have to pay for it out-of-pocket. however, it has been determined that the screening test is very valuable because the annual incidence of stroke among those who have been screened is nearly half that of the general population