Free PSA ELISA Kit (Prostate Specific Antigen)


Human free PSA ELISA kit is designed for detecting in vitro quantitative concentrations of free prostate specific antigen (free PSA, f-PSA, gamma-seminoprotein, kallikrein-3) in human plasma and serum. This assay has a minimum sensitivity limit of 0.1 ng/ml.


Prostate specific antigen (PSA) is also referred to as kallikrein-3 (KLK3) or gamma-seminoprotein, it is a tissue specific protein that is not solely tumor specific. It is commonly used as one of the most important markers for prostate carcinoma, where it is displaying higher specificity when compared to other biochemical markers that are used for this application (such as carcinoembryonic antigen, PAP and total alkaline phosphatase). In recent time the measurement of serum PSA levels is becoming the general accepted method in order to improve the diagnostic specificity of digital rectal examination.

Prostate specific antigen is an enzyme which has the ability to bind to proteins in the semen and also to break them down, this process results in the semen becoming more liquid. This can also help the sperm move more easily through the women’s fallopian tube during reproduction. Some PSA is able to pass into the bloodstream via the rich blood supply of the prostate. Essentially there are three major forms of prostate specific antigen that can be distinguished, however, only two are immune reactive. The predominant form is the one which is a complex with α1-antichymotrypsin and a small amount which is not protein bound is known as free PSA (only represents about 10 – 40% of the immunologically detectable prostate specific antigen.


All reagents supplied need to be stored at 2 °C – 8 °C, unopened reagents will retain reactivity until expiration date. Do not use reagents beyond this date.

  • Microtiterwells: Coated with anti-free PSA antibody (monoclonal).
  • Zero Standard
  • Sample Diluent.
  • Standard (1-5): Concentrations 0.75, 1.5, 3.0, 6.0, 12.0 ng/mL. The standards are calibrated against NIBSC (WHO) Standard 96/668.
  • Control Low.
  • Control High.
  • Assay Reagent.
  • Enzyme Conjugate: Anti-PSA antibody conjugated to horseradish peroxidase.
  • Substrate Solution: Tetramethylbenzidine (TMB).
  • Stop Solution.
  • Wash Solution (40x Concentrated).


The minimum detection sensitivity level of free prostate specific antigen (kallikrein-3, free PSA, gamma-seminoprotein) using current free PSA ELISA kit was 0.1 ng/ml. The dynamic range for this assay is 0.75 – 12.0 ng/ml.


– Detection limit: 0.1 ng/mL
– Intra-Assay Precision: 6.1 – 7.7%
– Inter-Assay Precision: 6.1 –7.8%
– Recovery: 91.8 – 116.0%
– Hook Effect: No hook effect has been noticed with samples up to 5000 ng/mL free PSA.
– Specificity: The assay is highly specific for free PSA, with a relatively low cross-reactivity to other proteins and polypeptides, lipids or chemotherapeutic agents that might be present in patient samples.


  1. The role of free-prostate specific antigen in prostate cancer detection. Curr Urol Rep. (2000) 1 (1): 78-82. Review. Han M., et al.
  2. Clinical utility of measurements of free and total prostate-specific antigen (PSA): a review. Prostate Suppl. (1996) 7: 64-9. Review. Catalona W.J.
  3. Cost-effectiveness of percent free PSA for prostate cancer detection in men with a total PSA of 4-10 ng/ml. Urol Int. (2007) 79 (4): 336-44. Bermúdez-Tamayo C., et al.
  4. Prostate cancer biomarkers: an update. Urol Oncol. (2014) 32 (3): 252-60. Review. Romero Otero J., et al.
  5. Percent free-prostate specific antigen: entering a new era in the detection of prostate cancer. Mayo Clin Proc. (1997) 72 (4): 337-44. Review. Vashi A.R. and Oesterling J.E.


  • Full Name: Free PSA ELISA Kit (Prostate Specific Antigen)
  • Reactivity: Human
  • Sample Type: Serum, Plasma
  • Sensitivity: 0.1 ng/ml


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