Human C Reactive Protein ELISA Kit (CRP) (ab99995)

The shelf life of each of our kits is indicated in the individual protocol booklet.

ab99995 may be stored for up to 6 months at 2 to 8°C from the date of shipment. Standard (recombinant protein) should be stored at -20°C or -80°C (recommended at –80°C) after reconstitution. Opened Microplate Wells or reagents may be store for up to 1 month at 2 to 8°C. Return unused wells to the pouch containing desiccant pack, reseal along entire edge. Note: the kit can be used within one year if the whole kit is stored at -20°C. The same is true for ab100610 and ab113326.

The lab sent the following comments and questions. Please let me know if you have the answers to those. I think the lab is trying to understand where exactly the problem might lie.

But I still think the standard curve should look better than what you had obtained the first time. Could you try the standard curve with the new kits you had sent and maybe a few sample dilutions - just to get some preliminary data?


Lab response:
Thank you for the update. In this recent test, none of the absorbances are high enough above background to be considered as real signals. As stated by the customer, this may have been due to using the already reconstituted antibody from the day before. With this being said, the first two tests did show very strong and consistent standard curves. The highest OD reading of ˜1.67 is definitely strong enough for creating a wide enough standard curve to incorporate a range of sample absorbances. Therefore, we do not believe this is a kit or lot related issue. The unfortunate conclusion may be that the amount of CRP in the cell lysate samples is simply too low to be detected by the ELISA kit. I understand the frustration of the customer for not obtaining useful data from the samples and if there truly is high amounts of this protein in the samples, there may be certain sample preparation issues that are contributing to them not being detected.

How were the HepG2 cells prepared?
Did the lysis buffer used contain any denaturing or reducing agents?
How long were the samples stored for before testing?
Were there any freeze-thaw cycles?



Thank you so much for your help and understanding.

Thank you so much for the additional information. I'll pass it on to the lab.

Should they have more suggestions, I will let you know.

I hope the 2 new kits will work as expected.

Please let me know if you have further questions.

Thank you for your emails.

I apologize that I could not get back to you earlier, but our office was closed over the holidays.

I am very sorry to hear that your effort and attempts to try to get the kits to work were unsuccessful. I will pass your comments on to the lab for their consideration.

In the meantime, I have arranged for a free of charge replacement for the 2 kits with another, newer lot number. The order number is xxx, and you should receive the 2 kits tomorrow.

I really hope the new kits will work as expected and they will be helpful for finishing your research before graduation

Please also do let me know if you have more questions and how the new kits are working for you.

Best of luck to you!

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. It has not been possible to obtain the single component of the kit from our source in this case, I have issued a free of charge replacement of the kit with the order number 1208938.

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.

When the new kit is used, it would be beneficial to briefly centrifuge the HRP-streptavidin vial before opening to ensure maximum recovery (Sometimes the liquid can adhere on the sides and cap of the vial).

Since excess volume of the HRP-streptavidin is provided, please inform the customer that 40ul of the HRP-streptavidin is still more than enough to complete the entire microplate. 40ul X 300 = 12ml of 1X working HRP-streptavidin solution. (Only 9.6ml is needed.) Please encourage the customer to use their current HRP-streptavidin vial and also remind them to centrifuge the vial before opening to ensure maximum recovery (if not doing so already).

Thank you for your help and cooperation in this case. Please let me know if you have any further questions.

Thank you for your patience.
I have heard back from the lab today with the following response:

"I am not quite sure what exactly the issue is with the standard curve. I plotted the values in a linear regression model and curve looks fine, see attachment. The highest standard signal strength is strong at ˜1.6 OD, the linearity is high (R2 >0.98), the background is low (0.08 OD), and the duplicate CV is low. Overall I’d say the standard curve is acceptable.

The customer is missing the 22.22 pg/ml and 7.407 pg/ml standard points though so I would certainly recommend the customer loads these. I’m also a little confused about the ODs for the 6.66 pg/ml and 2.469 pg/ml – were the OD values measured exactly the same value? This seems unlikely.
The issue to me seems not to be the standard curve but that the sample ODs are very low (0.8 OD) which is below detection, near background. There are a few different options the customer could try in order to get their sample signals within the detectable range of the assay.
Performing the sample/standard incubation overnight at 4ºC with gently rocking.
Increase amount of biotinylated detection antibody (by 1.5 fold or so – too much may increase background)
Increase amount of HRP-streptavidin (by about 1.5 fold or so – too much may increase background)
Concentrate the sample in a non-denaturing method (for example, using a chilled spin column)

Please note: it’s best to try just one of these modifications at a time. Implementing too many of these changes at once may cause high background."



I replied to the lab regarding the standard curve, but please let me know if these tips will be of help and improve your results.

You might not need to dilute your samples by a factor of 10. Maybe try undiluted samples and a dilution by factor of 2 and 4.

I hope this information is helpful to you. Please do not hesitate to contact us if you need any more advice or information.

Free Rabbit monoclonal antibody with any purchase of a primary antibody, while stocks last! Quote “RABMAB-XBSMG” in your next primary antibody order. For more information, visit the following link: https://www.abcam.com/index.html?pageconfig=resource&rid=15447

Thank you for your phone message.

I have emailed the lab yesterday but have not yet heard back. I will follow up with them today.

As for the antibody vial:

Item F detection antibody comes as a very concentrated, small volume liquid. Usually the volume is very small, ˜2ul, so it may be difficult to see. This is why we recommend customers spin down the vial before use to ensure no liquid has adhered to the inside cap or sides of the vial. The small volume is also the reason the biotinylated antibody solution is prepared inside the vial and why the customer should not try to pipette the 1-2ul out.

I hope this information is helpful to you. Please do not hesitate to contact us if you need any more advice or information.

Free Rabbit monoclonal antibody with any purchase of a primary antibody, while stocks last! Quote “RABMAB-XBSMG” in your next primary antibody order. For more information, visit the following link: https://www.abcam.com/index.html?pageconfig=resource&rid=15447

Thank you for your message. I am sorry to hear there was a shortage of the HRP-streptavidin concentrate item in the ab99995 kit.

If this has been purchased in the last 6 months, I will be pleased to provide a replacement of this component. In order for me to arrange this, please confirm the order number and date of purchase.

Thank you for your cooperation. I look forward to hearing from you.

Thank you for contacting us.

This is very normal, the buffer contains proteins which gets precipitated at low temperature. Please keep the buffer at room temperature for few minutes and then vortex it. The white opaque residue will go away.

The kit is absolutely fine so please use it without any hesitation.

I hope this information is helpful to you. Please do not hesitate to contact us if you need any more advice or information.

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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.

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.