An ultrasensitive immunoassay for prostate-specific antigen based on conventional colorimetric detection.
OBJECTIVE
Development of an ultrasensitive immunoassay for serum PSA involving conventional detection probes.


METHODS
The assay involves a polyclonal antibody immobilized in microtitration wells and a monoclonal antibody labeled with horseradish peroxidase. In a one-step assay, the enzymatic activity of the bound detection antibody is monitored by the addition of hydrogen peroxide/tetramethylbenzidine substrate reagent followed by spectrophotometric quantification of the conversion product.


RESULTS
The assay has a lower detection limit of 0.003 micrograms/L, biological detection limit of 0.009 micrograms/L, and intra- and interassay CVs of 8.2% and 10.5% at PSA concentrations of 0.022 and 0.065 micrograms/L, respectively. The recovery of the assay averaged 104% and it demonstrated a dilution linearity down to at least 0.01 micrograms of PSA/L. Results of comparison data correlated well with those obtained by a well established enzyme immunoassay. The serum PSA concentrations were < 0.012 micrograms/L in the majority of patients (53.8%) who had undergone radical prostatectomy.


CONCLUSIONS
This assay is well suited for post-surgical monitoring of PSA in patients with prostate cancer.
Khosravi
M J
MJ
Diagnostic Systems Laboratories (Canada) Inc., Toronto, Ontario.
Papanastasiou-Diamandi
A
A
Mistry
J
J
D000906:Antibodies; D000911:Antibodies, Monoclonal; D005591:Chemical Fractionation; D003124:Colorimetry; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D008297:Male; D009195:Peroxidase / Q000032:analysis; D017430:Prostate-Specific Antigen / Q000097:blood*; D011468:Prostatectomy
D000906:Antibodies; D000911:Antibodies, Monoclonal; D009195:Peroxidase; D017430:Prostate-Specific Antigen