I had the same issue with Backup method for solid phase when I came to work for this hospital. They used N-hance (a modified LISS) for all tube reactions. Whenever they had panagglutination they would run a tube N-hance screen. The problem was I couldn't get the correlation to match the Echo's sensitivity. Finally I ordered PeG and ran correlation with all three ( Echo-capture, PeG, N-hance) with 20 known positive antibodies. While the Echo reactions were much stronger, I was able to get all positives to react with PeG( some very weak) while the N-hance I had only a ~50% reaction rate. We would miss over half of all "true" antibody reactions using N-hance. I converted us completely to using PeG only for tube.