Human PSA ELISA Kit (KLK3) (ab113327)

Assay diluent A is is only required for the preparation of the standards and samples, if your samples are plasma. Once the PSA is captured on the plate and the samples and standard solutions are discarded from the wells, the remainder of the assay does not require diluent A, and diluent B, a buffer, should be used for diluting the reagents.

Thank you for contacting us. Your credit note ID is . I am sorry that this antibody did not perform as stated on the datasheet. If payment has already been made on the original order and you wish to receive a refund, please ask your purchasing department to contact our accounting department so that we may gather the correct information needed for the refund. To avoid confusion, please ensure your accounts department is aware of how the credit note is being used. Our accounting department can be contacted by email at us.credits@abcam.com or by telephone using the information at the Contact Us link in the top right corner of our website. Please refer to the credit note ID in any correspondence with our accounting department. The credit note ID is for your reference only and does not automatically guarantee the credit. I hope this experience will not prevent you from purchasing other products from us in the future. Our Scientific Support team is always at your service, should you require further expert advice.

Thank you for confirming these details and for your cooperation. The details provided enable us to closely monitor the quality of our products. I am sorry this product did not perform as stated on the datasheet and for the inconvenience this has caused. As requested, I have issued a free of charge replacement with the order number To check the status of the order please contact our Customer Service team and reference this number. Please note that this free of charge replacement vial is also covered by our Abpromise guarantee. Should you still be experiencing difficulties, or if you have any further questions, please do not hesitate to let us know. I wish you the best of luck with your research.

Thank you for your message and for providing this further information.

I am sorry to hear the suggestions made have not improved the results on this occasion. I appreciate the time you have spent on these experiments, and would like to offer a you a free of charge replacement, or a refund/credit note in compensation (providing the product has been purchased in the last 120 days). In order to arrange this, I would appreciate if you could confirm your order number and date of purchase?

Thank you for your continued cooperation. I look forward to hearing from you with details of how you would like to proceed.

Thank you for your response.

I am sorry that the initial suggestion that I was able to give and that these further suggestions did not improve blank reading and thereby the detection limits of this for you. Would you be willing to send me the data, including your standard curves that you collected using our kit? This information will be of great help to us in monitoring the quality of our products and in our internal tests.

I hope that this information is helpful. Please let me know if you have any questions or there are other ways that Abcam may help you meet your research goals.

Thank you for contacting Abcam regarding your higher 0 reading.

I have had a chance to speak with the lab regarding this. Their reply follows:

In general, a 0 standard OD reading around 0.2 OD is not considered very high but is in that gray area between low and high background. What dilution factor is the customer using? FYI, our recommended serum dilution for this kit is 2-fold.

The sensitivity limit for this kit is 8pg/ml (which is actually quite sensitive) and based on a recommended 2-fold dilution, PSA must already be a pretty low abundant protein in normal serum, so it isn’t too surprising that the sample ODs are low if they are testing normal serum as well. Therefore I don’t think the issue here is high background or anything procedural, the concentration of PSA in the customer’s samples is likely just at very low levels, near the limit of detection.

The problem with trying to reduce the background and also increase the sample signal strength is that these two factors counteract each other. For instance, extra washing will lower the background but will also decrease the overall plate signal, including the samples. On the other hand, performing a longer standard/sample incubation will increase the standard/sample signals but then will also increase the background.

For cases like these, it is important that the samples are centrifuged very well before loading onto the assay to help remove any particles or particulates that could be inhibiting detection. Making sure that the wash buffer iscompletelyremoved from all of the wells after each step is also important to keep the background low and increase the chances of getting the maximum sensitivity.

I don’t believe you will be able to lower the background too much more but if you want to try, below are tips they can keep in mind. If all else fails, you may want to consider using a different sample type, such as plasma or another body fluid.

Ultimately it may be that the PSA concentration in these samples is below the detection limit, which again is pretty low at 8 pg/ml.



Causes of High Background



Too much HRP-Streptavidin may cause background. Briefly centrifuge the vial of HRP-streptavidin concentrate (Item G) and pipette up and down to mix gently before using, since precipitation may form during storage.
Too much detection antibody may also contribute to high background. Make sure ofcorrect dilution foldof both the biotinylatedantibody (Item F) and HRP-Streptavidin. Both should be diluted with 1x Assay Diluent B.
Long incubation times in some steps (i.e. overnight incubation) can cause high background.
And finally, the wash steps may introduce background: if the plate is insufficiently washed, or if the wash buffer itself was contaminated. Wash buffer must be removed completely from the wells after each wash. We recommend using an automated plate washer or multi-channel pipettor. Squirt bottles are not advised.





If the high background persists after checking all these steps, try reducing the amount of HRP-streptavidin (by increasing the dilution by 1.5 or 2-fold).



I hope that this information is helpful. Please let me know if you have any questions or there are other ways that Abcam may help you meet your research goals.

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Date d’expiration : 09. Juillet 2012

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Thank you for your inquiry. Although our production team does not’t routinely test urine samples,we know this kit is suitable for urine samples (based on our past experience with it). This is a general guideline on preparation of urine for ELISA testing: Collect samples without adding stabilizers. Spin down the samples hard (e.g. 10000 x g for 1 min or 5000 x g for 2 min). Aliquot, quick freeze in dry ice/methanol bath, and store at –80C until use. We would also recommend starting with a minimal dilution of the urine sample (such as 2-fold), since in our experience, PSA levels are often very low in urine (0.12-3.72ng/ml). This has not been experimentally tested by us for this specific kit and the customer has to determine the optimal dilution experimentally. I hope this information is helpful. Please do not hesitate to contact me with any further questions in this matter.