Ultrasensitive time-resolved immunofluorometric assay of prostate-specific antigen in serum and preliminary clinical studies.
We developed an ultrasensitive method for measuring prostate-specific antigen (PSA) in serum. The assay includes a capture monoclonal anti-PSA antibody coated to microtiter wells, a biotinylated rabbit polyclonal detection antibody, and alkaline phosphatase (ALP)-labeled streptavidin. The activity of ALP is measured with the substrate diflunisal phosphate; the released diflunisal forms highly fluorescent complexes with Tb(3+)-EDTA that are quantified with microsecond time-resolved fluorometry. The assay is precise and accurate and correlates well with the established Hybritech Tandem-PSA kit. Its distinguishing feature is extreme sensitivity (lowest limit of detection is 0.002 micrograms/L or 2 x 10(6) PSA molecules per assay). This is the most sensitive PSA assay reported thus far; we used it to quantify PSA in patients who had undergone radical prostatectomy. Many patients had < 0.01 micrograms/L PSA in their serum. This method could have important clinical applications in postsurgical early detection of relapse or residual prostate cancer, as recently suggested in the literature (Clin Chem 1992;38:1930-2).
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Department of Clinical Biochemistry, Toronto Hospital, Ontario, Canada.
Diamandis
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D000293:Adolescent; D000328:Adult; D000368:Aged; D000469:Alkaline Phosphatase; D000911:Antibodies, Monoclonal; D002851:Chromatography, High Pressure Liquid; D004492:Edetic Acid; D005260:Female; D015200:Fluoroimmunoassay / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis; D017430:Prostate-Specific Antigen / Q000097:blood*; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D011786:Quality Control; D012016:Reference Values; D012680:Sensitivity and Specificity; D013725:Terbium
D000911:Antibodies, Monoclonal; D013725:Terbium; D004492:Edetic Acid; D000469:Alkaline Phosphatase; D017430:Prostate-Specific Antigen