Longitudinal analysis of serial measurements of free and total PSA among men with and without prostatic cancer

Five-Year Stability Study of Free and Total Prostate-Specific Antigen Concentrations in Serum Specimens Collected and Stored at – 70°C or Less

“…In support of this, we have offered evidence in this study, by evaluating the tPSA(2006)/tP-SA(2001) and fPSA(2006)/fPSA(2001) ratios of 2 subgroups of our 160 specimens (i.e., those stored for <12 months and >12 months prior to initial testing), which strongly suggests that a pre-test storage time of up to 22.9 months at -70ºC or lower temperature does not deleteriously affect the stability of either tPSA or fPSA. Our use of tPSA and fPSA values, obtained on initial assay of the sera in 2001, as baseline values for this 5-year study was justified based on previous studies demonstrating the stability of PSA at these storage temperatures (9,16,(19)(20)(21) and on our independent analysis showing that there was no difference in the tPSA(2006)/tPSA(2001) and fP-SA(2006)/fPSA(2001) ratios of 2 specimen subgroups stored for <12 months and >12 months prior to initial testing. Specimen storage bank temperatures were and continue to be monitored daily at DOCRO to ensure proper temperature control.…”

“…Approximately one third of men in this age group with tPSA levels between 4.0 and 10.0 ng/mL have biopsy-proven PCa; tPSA levels greater than 10.0 ng/mL indicate biopsy-proven PCa in the majority of men who do not have an underlying infection of the prostate (4). The percentage of fPSA found in serum taken imme-diately prior to biopsy of the prostate has been demonstrated by numerous studies to be lower in men with PCa (5, 6) and evaluation of the pre-biopsy f/tPSA ratio has improved the sensitivity and specificity of PSA testing (7)(8)(9). A f/tPSA ratio of less than 10% has been shown to be highly indicative of PCa, whereas a fPSA of greater than 25% has been demonstrated to be highly indicative of benign disease of the prostate (10)(11)(12)(13)(14).…”

Prostate specific antigen: biology, biochemistry and available commercial assays

“…122 Computer modelling with logistic regression analysis shows that, for a patient with a normal digital rectal examination (DRE), a t-PSA of 3 mg/L and a PSA index of 10%, the probability of prostate cancer is 30%, rising to 50% with an index of 5% at the same t-PSA concentration. 123 Catalona et al 124 observed that, for a standard 90% detection rate, the discriminant PSA index of 13% for a prostate gland of less than 40 g needed to increase to 21% for glands over 40 g. Pearson et al 125 showed that, whilst the PSA index remains stable with increasing age, it is signi®cantly lower in men with prostate cancer than in normal individuals and men with BPH, and that this may be apparent for up to 8 years prior to diagnosis.…”

Day to day changes in free and total PSA: significance of biological variation

“…8,20 The physiological stability of PSA levels unrelated to changes in pathological processes is an important factor that could bias the usefulness of yearly PSA determination. This study showed that short-term biological variation was substantial in the majority of men, and that interpretation of the change in total or percent freeatotal PSA levels should take into account the change due to biological and analytical variation.…”