Intraindividual variation of PSA, free PSA and complexed PSA in a cohort of patients with prostate cancer managed with watchful observation

• Published in: Clinical biochemistry Vol. 35; no. 6; pp. 471 - 475
• Main Authors: Bunting, Peter S, DeBoer, Gerrit, Choo, Richard, Danjoux, Cyril, Klotz, Laurence, Fleshner, Neil
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2002
• Subjects: Cohort Studies; Complexed PSA; Disease Progression; Free PSA; Humans; Intraindividual; Male; Neoplasm; Neoplasm Staging; Prostate; Prostate-Specific Antigen - analysis; Prostate-Specific Antigen - metabolism; Prostatic Neoplasms - classification; Prostatic Neoplasms - metabolism; Prostatic Neoplasms - pathology; PSA; Sensitivity and Specificity; Time Factors; Variation; Neoplasm; Complexed PSA; Intraindividual; Free PSA; Variation; Prostate; PSA
• ISSN: 0009-9120; 1873-2933
• DOI: 10.1016/S0009-9120(02)00345-4

To determine the intraindividual variation of prostate-specific antigen (PSA) isoforms in prostate cancer patients managed conservatively with watchful observation. Patients with favorable clinical parameters (stage T1b-T2b N0 M0, Gleason score ≤ 7, and PSA ≤ 15) were recruited to participate in a watchful observation program. Specimens were drawn for measurement of total (tPSA), free (fPSA) and complexed (cPSA) prostate-specific antigen isoforms. Total biologic variation and between-day analytical variation were used to calculate intraindividual variation. Total variation for each isoform and two ratios were not greatly affected by the time window for measurements in the interval 6 months to 2.7 yr. Analytical variation made only a small contribution to the total biologic variation. Intraindividual variation for a 1-yr time interval for tPSA, fPSA, cPSA and the ratios of fPSA and cPSA to tPSA was, respectively, 21.6, 19.3, 25.4, 20.0 and 13.1%. The amount of change required for a significant difference between two readings (with 95% confidence) was, respectively, 59.8, 53.4, 70.4, 55.3 and 36.2%. There is a significantly higher intraindividual variation of cPSA (25.4%), and a significantly lower intraindividual variation of the ratio cPSA to tPSA (13.1%) compared to the other individual PSA isoforms and to the ratio of fPSA to tPSA. The amount of change required for a significant difference between two concentrations is large for all variables studied, but the lowest is the ratio of cPSA to tPSA (36.2%). These results have significance for diagnosis and monitoring of patients with prostate cancer.