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Does psoralen interfere with bead assays? 
Posted: 17 March 2009 12:27 PM   [ Ignore ]  
Total Posts:  9
Joined  2008-10-09

This is an archive from the old ASHI Forum


William W. Ward

Posted: Wed May 21, 2008 2:03 pm Post subject: Does psoralen interfere with bead assays?  Reply with quote
There have been no other posts to this section of the ASHI forum, so as moderator, I’d like to kick things off with a question.

For labs whose heart and/or lung transplant programs use photophoresis on highly sensitized patients, have you seen depressed positive control (PC) bead and elevated negative control (NC) bead responses in the OL LABScreen single antigen assays when testing serum from these patients? We are seeing squirrely results on the first two highly sensitized patients one of our centers is treating with photophoresis. I’m thinking it may have something to do with the drug used (methoxypsoralen) to sensitize cells to UV irradiation. Can anyone tell me if psoralen binds directly to plastic (i.e. the Luminex bead) and/or fluoresces such that it could either increase the MFI signal or quench it? Any insight would be greatly appreciated. We also see paradoxical results when we try AbsorbOut on these patient’s sera.

Thanks - Bill Ward



Posted: Wed May 28, 2008 3:53 pm Post subject:  Reply with quote
We’ve seen “plastic” antibodies, as we call them on several patients.
Usually dialysis patients, sometimes pregnant women( non-transplant, non-dialysis).
We don’t do heart patients yet, so I don’t know about that.
Some of the Immunology tests we have non-specific matrix binding only on a very few patients, but haven’t found a pattern yet.


William W. Ward

Posted: Thu May 29, 2008 12:03 pm Post subject:  Reply with quote
Marilyn -

This phenomenon in the sensitized heart patients on photophoresis does not appear to be the often-seen anti-albumin or anti-plastic (so-called “antibead") antibodies. That is why I am curious about being related to the presence of psoralen.