We are validating an Ortho Vision and considering whether to use it for doing gel titrations. We have been doing tube titrations up to this point. We ran one today on which the Vision recorded the result of the last positive dilution as 1+ but if we read the gel card manually we would call it W+ not 1+. That would change the titer result. The reaction the machine called 1+ appears significantly weaker than the photos in the Interpretation Guide showing various 1+ reactions (but strong enough to be called a true positive). The instrument requires results review (not necessarily manual review of the card itself) of any positive reaction 1+ or weaker. Is anyone else using the Vision for titrations? Have you seen anything similar? How would you determine the titer in such a a case?
Background information: This antibody is suspected to be RhIG but they had no record of a negative screen in this pregnancy. We suspect that they plan to follow titers to make sure they are dropping. The saline/IgG tube titer is 2 (in gentle, experienced hands-- but the 1:4 dilution tube was W+). The Vision gave a 16 if that well was called 1+ (8 if it was changed to negative--there is no choice for W+ on the analyzer).