Complexed PSA: This test directly measures the amount of PSA that is attached to other proteins (the portion of PSA that is not "free"). This test could be done instead of checking the total and free PSA, and it could give the same amount of information, but it is not widely used. Over the past years, the assessment of equimolarity has been typically performed by the characterization of the recovery of IS 96/670, consisting of 90% PSA-ACT and 10% PSA free form, by marketed PSA assays. The most promising approach to improve the specificity of PSA, particularly in the range lower 10 ng/ml, is the measurement of molecular isoforms of PSA. These are the disengaged free PSA (fPSA) and the complexed PSA (cPSA) bound to α1-antichymotrypsin. Complexed PSA alone did not enhance the overall diagnostic accuracy compared with percent free PSA in the Hybritech total PSA range between 4.01 and 6.00 ng./ml., between 6.01 and 10.00 ng./ml., and between 2.50 and 6.00 ng./ml. Complexed PSA test measures both PSA that is floating freely in the blood and PSA that is attached to other proteins in the blood. PSA levels rise with age, and men of different ethnicities may have naturally higher PSA levels, so discuss with your doctor what a healthy PSA level looks like for you. In addition, previous attempts to measure complexed PSA (PSA±ACT: PSA bound to a-1-antichymotrypsin) have been limited to the high cross reactivity of the monoclonal antibodies to other ACT .

complexed psa vs free psa