Complexed PSA can help guide Tx of men with low total PSA. (Results of Multicenter Study).

ORLANDO, FLA. -- Measuring complexed prostate-specific antigen is more specific and just as sensitive as measuring total PSA for detecting prostate cancer in men with total PSA levels between 2 and 4 ng/mL.

Those were the findings of a multicenter study that was presented at the annual meeting of the American Association for Clinical Chemistry.

Complexed PSA is a molecular form of PSA that becomes elevated in men who have prostate cancer. Free PSA predominates in healthy men. Together, these two forms compose the total PSA measure.

Researchers initially evaluated 813 men with a median age of 63 years. The patients were scheduled for first-time prostate biopsy at seven clinical centers. The majority (78%) of the participants were tracked prospectively; the remaining cases were retrospective and were included in the study to increase its statistical power.

Most of the participants (88%) were white, while 6% were black and 6% were of unknown ethnicity The small number of nonwhite patients did not permit assessment of PSA values based on ethnicity.

After blood samples were drawn and analyzed, the 215 men who had a total PSA value between 2 and 4 ng/mL underwent further evaluation.

"We found a significant number of cancers in the 2- to 4-ng/ mL range," said Carol Cheli, staff scientist at Bayer Diagnostics, Tarry-town, N.Y