Stability of free prostate-specific antigen in serum samples under a variety of sample collection and sample storage conditions.

Author(s): Woodrum D, French C, Shamel LB

Publication: Urology, 1996, Vol. 48, Page 33-9

PubMed ID: 8973697 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   The purpose of this study was to characterize the impact of allowing blood to clot at RT for different amounts of time before preparing serum samples for total and free PSA value determination. For this study, blood specimens were obtained from 11 different subjects, and serum was snap-frozen at -70 degrees C.

   Summary of Findings:

   While total PSA values stayed the same, free PSA values decreased at an average rate of 1% per hour of clotting time at RT (P=0.0001).

   Biospecimens

   • Bodily Fluid - Serum
   • Bodily Fluid - Blood

   Preservative Types

   • Frozen

   Diagnoses:

   • Prostatitis
   • Neoplastic - Carcinoma
   • Neoplastic - Benign

   Platform:

   Analyte	Technology Platform
   Glycoprotein	Immunoassay

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Time at room temperature	1 h 3 h 5 h 8 h
   Biospecimen Aliquots and Components	Centrifugation	Centrifugation delays investigated

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2. Study Purpose

   The purpose of this study was to determine the effects of storing serum samples at RT or 4 degrees C over time on total and free PSA levels. 12 subjects were included in this study.

   Summary of Findings:

   Total PSA values were unaffected when stored at 4 degrees C for one week. However, free PSA levels decreased by an average of 3.3% per day (P=0.0001). When serum samples were stored at RT, total PSA levels decreased by an average of 0.9% per day (P=0.0002). Interestingly, free PSA levels decreased by an average of only 1.9% per day (P=0.0034) at RT, which is less than the decline observed at 4 degrees C. The authors note that this was an unexpected result.

   Biospecimens

   • Bodily Fluid - Serum

   Preservative Types

   • None (Fresh)
   • Other Preservative

   Diagnoses:

   • Prostatitis
   • Neoplastic - Carcinoma
   • Neoplastic - Benign

   Platform:

   Analyte	Technology Platform
   Glycoprotein	Immunoassay

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Preservation	Type of fixation/preservation	None (fresh) Refrigeration
   Storage	Storage temperature	RT 4 degrees C
   Storage	Storage duration	0 d 1 d 2 d 7 d
   Storage	Time at room temperature	30-60 min

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3. Study Purpose

   The purpose of this study was to examine the effects of freeze-thaw cycling on the amount of total and free PSA found in serum specimens from 4 different subjects.

   Summary of Findings:

   Total PSA and free PSA values were unaffected by freeze-thaw cycling.

   Biospecimens

   • Bodily Fluid - Serum

   Preservative Types

   • Frozen

   Diagnoses:

   • Prostatitis
   • Neoplastic - Carcinoma
   • Neoplastic - Benign

   Platform:

   Analyte	Technology Platform
   Glycoprotein	Immunoassay

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Freeze/thaw cycling	1 cycle 2 cycles 3 cycles 4 cycles 5 cycles
   Storage	Time at room temperature	30-60 min

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4. Study Purpose

   The purpose of this study was to examine the effects of long-term storage at either -20 or -70 degrees C on the amount of total and free PSA found in serum specimens. This study was performed first with 11 subjects, and then separately with 18 additional subjects. Notably, data from the second cohort was not collected at 12 months for either storage temperature. Furthermore, the samples stored at -70 degrees C were first tested at 3 months, rather than 0 months.

   Summary of Findings:

   Total PSA values were unaffected when serum was stored at -20 or -70 degrees C for one year. However, free PSA levels decreased by an average of 0.9% per month (P=0.0001) when serum was stored at -20 degrees C and 0.4% per month (P=0.0001) at -70 degrees C.

   Biospecimens

   • Bodily Fluid - Serum

   Preservative Types

   • Frozen

   Diagnoses:

   • Prostatitis
   • Neoplastic - Carcinoma
   • Neoplastic - Benign

   Platform:

   Analyte	Technology Platform
   Glycoprotein	Immunoassay

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Storage temperature	-20 degrees C -70 degrees C
   Storage	Storage duration	0 months 3 months 6 months 9 months 12 months
   Storage	Time at room temperature	30-60 min

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