Advantages of replacing the total PSA assay with the assay for PSA-α1-antichymotrypsin complex for the screening and management of prostate cancer

Abstract

Several advantages become immediately apparent when the prostate specific antigen (PSA, or tPSA) assay is replaced by the assay specific for the serum PSA‐α1‐antichymotrypsin (PSA‐ACT) complex. For instance, random contributions to the tPSA value by various serum minor PSA isoforms can be avoided, making possible the determination of a more accurate relation of the PSA‐ACT concentration to the tumor activity. Discrepancies in percent free PSA (% fPSA) values from the same specimens due to the use of different commercial kits also can be eliminated, mainly because the PSA‐ACT assay does not have the problems in antibody selection and calibrator preparation usually associated with the tPSA assay. We found that at the present time different cutoffs of % fPSA for the differentiation of BPH from prostate cancer must be established for each individual tPSA assay. Cutoffs established using values from one tPSA assay should not be used for making clinical decisions when their tPSA values are determined by a different kit. Moreover, when we monitored the patients during treatment with serum tPSA, specific fPSA, and specific PSA‐ACT complex assays simultaneously, it was clear that any interpretation of the patient's clinical status based on tPSA values alone could be misleading. Because there is less PSA‐ACT complex in BPH specimens relative to that found in cancer serum samples, expressing fPSA as “fPSA/PSA‐ACT × 100” and measuring PSA‐ACT complex concentrations instead of tPSA during screening improve the measurable contrast between BPH and prostate cancer. Although individually modest, collectively these advantages can add up to considerable improvements. J. Clin. Lab. Anal. 12:32–40, 1998. © 1998 Wiley‐Liss, Inc.

Complexed prostate-specific antigen improvement in detecting prostate cancer

“…The value of PSA-ACT changes independently of total PSA, which means that the change of PSA-ACT cannot be predicted by the change of total PSA. Wu and Liu [16] monitored the change of total, free, and PSA-ACT simultaneously in 11 men with prostate cancer. They observed that the change in total PSA differed from the change in PSA-ACT in six of 11 cases.…”

Komplexiertes oder freies prostataspezifisches Antigen: welche Komponente sollte zur Differenzierung zwischen benigner Prostatahyperplasie und Prostatakarzinom bestimmt werden?. Complexed or Free Prostate Specific Antigen: Which Component Should be Determined to Improve the Differentiation between Benign Prostatic Hyperplasia and Prostate Cancer?

“…Der Quotient aus fPSA zu tPSA scheint zur Zeit der geeignetste Parameter zur Differenzierung zwischen PCa und BPH zu sein [22][23][24]. Sowohl klinische als auch analytische Gründe sprechen jedoch für die Bestimmung des ACT-PSA anstelle des fPSA [25]. Das ACT-PSA bzw.…”

“…Dies ist u.a. dadurch bedingt, weil unspezifische Bindungen des ACT-Cathepsin G-Komplexes zur berbestimmung des ACT-PSA f hren [25,31]. Diese Probleme konnten in der Zwischenzeit weitgehend durch den Einsatz von spezifischen ACT-PSA-Antik rpern mit geringer Kreuzreaktivit t gegen ber ACT, fPSA und dem ACT-Cathepsin-Komplex [26,30,32] gelöst werden.…”