cPSA - Complex PSA Testing

Menstuff® has compiled the following information on Complex PSA Testing.

Background
What is cPSA?
How does cPSA work?
What are the unique benefits of cPSA?
Where is the cPSA test available?
cPSA or Free PSA?
References

Background


PSA is a glycoprotein produced almost exclusively by epithelial cells in the prostate. PSA exists in the blood in two forms: “free” (fPSA) which is not bound to protein and “complexed” (cPSA) which is bound. An elevated PSA may indicate the presence of prostate cancer (CaP). A biopsy is needed to confirm if cancer is present.

Total PSA (tPSA) is the most common PSA test used to detect CaP. However, tPSA has low specificity leading to high levels of false positives (indicating CaP was present when, in fact it was not) and false negatives (indicating CaP was not present, in fact, it was). In addition to expensive follow-up testing because of the high levels of false positives associated with PSA, and the corresponding anxiety, pain and inconvenience, research has focused on the development of enhanced serum tests.

What is cPSA?


Studies have shown that the majority of immunoreactive PSA in cancer patients is complexed with alpha-1-antichymotrypsin.1 The Bayer Diagnostics’ cPSA assay accurately measures PSA in complex with protease inhibitors. This assay has value in the discrimination of CaP from benign prostate disease, and in the monitoring of CaP following primary treatment.

How does cPSA work? †


Serum samples are evaluated in a laboratory to determine the level of cPSA. Concentrations of cPSA above 3.6 ng/mL are considered abnormal, which indicate the possibility of CaP.

What are the unique benefits of cPSA?


Accuracy: The Bayer Diagnostic cPSA assay provided a 10-22% improvement in specificity over a commercially available (tPSA), resulting in fewer false positives.2

Basic Math: Since tPSA is comprised of two basic components: cPSA (approximately 85% of total PSA in most cancer-free men) and fPSA (approximately 15% of total PSA in most cancer-free men) Bayer cPSA is a direct measure of the PSA form which is in greater proportion in men with CaP.1

Confidence: cPSA results will remain constant over time under normal sample handling.3,4 The instability of fPSA can lead to inaccurate measurement of the ratio of free to total PSA (f/t PSA) and result in an increase in false-positive results.5

Where is the cPSA test available?


cPSA assay is currently available in laboratories nationwide.

References


1 Stenman, et. al, A complex between prostate specific antigen and alpha-1-antichymotrypsin is the major form of prostate specific antigen in serum of patients with prostatic cancer: assay of the complex improves clinical sensitivity for cancer. Cancer Res. 1991;51; 222-226.

2 Okegawa, et. al, Comparison of two investigative assays for the complexed prostate specific antigen between 4.1 and 10.0 ng/mL. Urology. 2001;55(5): 700-704.

3 Allard, et. al, Multicenter evaluation of the performance and clinical utility in longitudinal monitoring of the Bayer Immuno 1 complexed PSA assay. Int J of Bio Markers. 1999;14(2): 73-83.

4 Jung, et. al, Different stability of free and complexed prostate specific antigen in serum in relation to specimen handling and storage conditions. Clin Chem Lab Med. 2000;38: 1271-1275.

5 Arcangeli, et al. Stability of serum total and free prostate specific antigen under varying storage intervals and temperatures. J of Urol. 1997;158: 2182-2187.

Source: www.pcaw.com/cPSA/index.asp  

 



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