Susannah

We totally agree that the instructions on the package insert should be strictly followed and the result of second spin should not be considered valid. However, a negative DAT and a positive auto control created a discrepancy needed to be solved. We took the negative result of second spin only as a reference. Actually we resorted to tube method. The results of tube method was rouleaux formation after immediate spin and 37 C incubation, but negative in indirect antiglobulin phase.

Yes, we've seen this phenomenon for once at our facility in Taiwan. Instead of (ID-MTS) Gel Test commonly used in US, we use ORTHO BIOVUE system column agglutination technology. The principles of these two systems are similar. We had a blood sample with a negative DAT, yet a positive autocontrol. Upon second centrifugation, the positive autocontrol turned to be negative. We then performed the autocontrol using tube method and found obvious rouleaux formation after immediate spin. We thus concluded that rouleaux formation of red blood cells might have caused a false positive reaction in CAT.