1. Presented by Chinelo P. Onyenekwu, M.D. and reviewed by Lorraine Blagg, MA, MLS(ASCP)^CMSBB, AHI(AMT)

A patient was admitted with an acute leukemia. They have no documented history of transfusion or transplantation. Specimens are sent to the blood bank for an ABO/Rh type, and initial testing requires additional work-up.

Initial ABO/Rh Typing:

Front Type				Reverse Type
Anti-A	Anti-B	Anti-D	Monoclonal Control	A1 cells	B cells
0	0	4+	0	0	3+

Extended ABO Typing
Forward

Front Type				Reverse Type
Anti-A	Anti-B	Anti-D	Monoclonal Control	A1 cells	B cells
0	0	4+	0	0	3+

Reverse

	A1 Cells	A2 Cells	B Cells	O Cells
RT	0	0	4+	0
4oC	W	0	4+	0

ABO Genotype TestingProbable ABO alleles: ABO*A/ABO*APredicted ABO phenotype: Group A

Medium resolution testing: ABO*A2, A3, AEL, and AW ruled out

Question: Based on the results from the testing shown below, what is the most likely cause of his ABO typing results?