Preanalytical Variables Influencing Free Prostate-Specific Antigen: Sample Storage Temperature and Duration

Abstract

Background: Though serum total Prostate-specific antigen (PSA) is the most important biological marker used for diagnosing Prostate cancer, its limitation has been lack of specificity. Total PSA has two fractions- free PSA and complexed PSA. Free PSA/total PSA ratio has increased specificity in diagnosing Prostate Cancer. It is unclear whether short-term storage of serum samples at commonly used temperature ranges in diagnostic laboratories has an impact on free PSA levels in serum. Objective: In this study our objective was to evaluate the stability of free PSA at temperature ranges- 4-80C and room temperature (23 - 280C) over 3 days. Methods: Study group consisted of 9 subjects from St. John's Medical College Hospital. Serum samples were analyzed for free PSA levels on Day 0 (baseline values), and after storage at room temperature (23-280C) and 4-80C on Days 1 and 3. Stability of serum total PSA levels over 3 days was evaluated using Pearson Correlation test. Results: Pearson Correlation Coefficient