Has there been any new literature on this issue?  We continue to see examples of reactive screens in Ortho gel, but negative when 3% screen cells are diluted to 0.8% with MTS diluent and run in gel.     

I retired recently so I do not have access to the product insert but I do remember that cells stored in LISS for longer periods can give some false positive reactions. Also, cold antibodies are enhanced by LISS so by diluted your 3% screen cells there is less time in LISS so less chance of false positives that can be experienced with older cells stored in LISS and also less chance of picking up a non specific cold antibody.  

The prediluted cells from Ortho contain the antibiotic nitrofurantoin as I recall.  I think that contributes to why they are to be kept in the dark as that drug is always dispensed in a brown bottle.  Patients make antibodies to the antibiotic and thus react in the prediluted cells.  Diluent 2 lacks preservatives because we can't store the suspensions over 24 hours so 3% cells suspended in it don't react with antibodies to the antibiotic because the antibiotic isn't present.  In my experience, the antibiotic doesn't seem to wash off of the cells but rather adheres to them.  What you are doing is a great way to prove that this is the problem rather than a cold antibody etc.  Most of our patients who have this, continue to have it for years to come.

We see this fairly often from our hospitals. Often the reactions have an abnormal appearance, as in they have mixed field or uniform haze through entire column, but the auto-control is negative. Usually we run a converted panel from another manufacturer and 4-6 random units. All of this testing is usually negative.