blood cross match

[joudi876]

I recently performed a crossmatch on a patient with blood type A negative, but accidentally I cross match it with A positive blood. According to my understanding, this should have resulted in a positive crossmatch indicating incompatibility between the donor blood and the patient. However, the result was negative. Can anyone help me understand why this may have happened, and whether there may have been any errors in my testing process?
Here are the steps I followed: I washed the donor cells three times, prepared a 5% red cell suspension, and performed an initial spin with recipient serum , which was negative. I then incubated the sample at 37 degrees for 15 minutes, centrifuged it, and washed it three times before adding 2 drops of Anti-Human Globulin (AHG) and centrifuging it again. However, the final crossmatch result was negative, which I understand is unexpected.