Frequently Asked Questions - PSA SemiQuant

  • The detection of seminal fluid is possible in cases where no spermatozoa can be found (for example vasectomized men).
  • Very small amounts of seminal fluid can be recorded. Studies of MACALUSO et al. (1999) showed, that an amount of only 10 μl sperm increased the PSA concentration in vaginal fluid ca. 200 fold.
  • PSA shows good stability. It can be detected on vaginal swabs up to 48 hours after intercourse and has been detected in 30 year old semen stains (Laux, 2009, personal communication).
  • PSA is a marker, which is more specific than the acid phosphatase test.
  • Studies have shown an increased extraction efficiency of PSA using a buffer in place of water (Laux, 2004). Seratec provides a buffer in the kit which ensures maximum extraction efficiency.
  • SERATEC® PSA Semiquant becomes a complete ‘ready-to-use’ product
  • No time is taken for your buffer make-up – save your valuable time!
  • Standard testing procedure for all users
  • Better comparability of results – no more variations of line intensity due to improper buffers or pH values
  • No false positives due to improper buffers or pH values
  • Uniformity of quantification by SERATEC® SeraQuant
  • The 4 ng internal standard allows the analyst to estimate the concentration of PSA in the sample and determine the likely method of analysis to obtain a DNA profile. Concentrations greater than 4 ng/mL may yield a nuclear DNA profile from nucleated cells in the seminal fluid whereas PSA values less than 4 ng/mL generally require Y-STR DNA analysis.

    PSA is now known to be found at very low levels in many different fluids and tissues including breast tissue and tumors, periurethral glands, breast milk, amniotic fluid and female urine. However, PSA levels in semen average 800,000 ng/mL. So by proper dilution of the sample, it is possible to determine that a positive result is unequivocally due to the presence of human seminal fluid.

    The SERATEC® PSA SEMIQUANT test is a chromatographic immunoassay (CIA) for the rapid semi-quantitative determination of PSA in body fluids. It contains two monoclonal murine anti-PSA antibodies as active compounds. One of these antibodies is immobilized at the test region on the membrane. The upstream control
    region and the region of the internal standard (between control and test region) contain immobilized polyclonal goat anti-mouse antibodies. The amount of antibody at the internal standard is adjusted to a level at which the line produced equates to a concentration of 4 ng PSA/mL. A glass fiber pad downstream of the membrane is used for sample loading and transmission to a second fiber pad with the dried and gold labeled second monoclonal murine anti-PSA antibody. PSA at the sample will bind to the remobilized gold-labeled antibody and form a PSA-gold-labeled-anti- PSA-antibody-complex. Through the capillary effect of the membrane, the reaction mixture including the complex is carried upwards with the fluid. In any case the colored gold labeled anti-PSA-antibody will bind to the anti-mouseantibody at the control region and the region of the internal standard thus developing two red lines (one at the control region ant one at the region of the internal standard). These two lines are independent of the existence of PSA in the sample and indicate only the correct execution of the test.
    If the sample contains PSA, the PSA-gold-labeled anti-PSA-antibody complex will bind to the immobilized monoclonal antibody of the test result region that recognizes another epitope on the PSA molecule (sandwich complex). The binding is indicated by the formation of an additional line. Thus a PSA positive sample will show three colored lines in the result window. The line in the middle (internal standard) correlates with an amount of 4 ng/ml PSA. In some cases it might be helpful to estimate the amount of PSA in the sample by comparison of the test result line with the internal standard line.

    PSA (Prostate-specific antigen) is a glycoprotein produced in the prostate and secreted into the seminal fluid. PSA is one of the major proteins in seminal fluid with concentrations of 0.2 to 3.0 mg/ml. Its main function is to liquefy the seminal fluid. This high amount and the fact that PSA is found only at very low concentrations in female vaginal fluid (0.4-0.9 ng/mL and 0.0-1.25 ng/mL, respectively) make PSA an interesting marker in forensic science for the detection of even small amounts of seminal fluid.