Development and evaluation of a new solid-phase direct immunoenzyme assay for prostatic acid phosphatase

Area of Science:

• Biochemistry
• Oncology
• Immunology

Background:

• Prostatic acid phosphatase (PAP) is a biomarker associated with prostate health.
• Accurate measurement of PAP is crucial for diagnosing and monitoring prostate conditions.

Purpose of the Study:

• To develop and validate a novel immunoassay for quantifying prostatic acid phosphatase (PAP).
• To assess the diagnostic utility of the PAP assay in distinguishing between healthy individuals, benign prostatic hyperplasia, and prostate cancer.

Main Methods:

• Utilized polystyrene-tube-attached rabbit antibodies against purified human prostatic acid phosphatase (PAP).
• Quantified immunoreactive PAP directly by its enzymatic activity within a solid-phase-bound immune complex.
• Determined assay sensitivity, precision (CVs), and organ specificity.

Main Results:

• The assay demonstrated a detection limit of 0.05 U/L (0.13 microgram/L) with CVs between 4.3-10.8%.
• Cross-reacting PAP activity was observed in kidney, leukocytes, and platelets, contributing to serum levels.
• Serum PAP activity varied significantly (up to 100%) diurnally and daily in healthy subjects.
• Established reference ranges for healthy individuals and those with benign prostatic hyperplasia.
• Achieved 65% sensitivity for detecting prostate cancer (stages A-D) in 33 untreated patients using a 90th percentile cutoff.

Conclusions:

• The developed PAP assay is sensitive and precise.
• Non-prostatic sources contribute to circulating PAP levels, necessitating careful interpretation.
• The assay shows promise as a tool for prostate cancer detection and therapy monitoring.