Table II.

Available methods and approaches to determine blood group antigens in patients transfused within the preceding three months.

Approach	Strengths	Weaknesses
Historical RBC phenotype	Not affected by recent transfusion. Can be universally applied to all patients. Helpful to avoid problems with evanesced alloantibodies on record at other facilities.	Clerical errors in communication. Unlikely to be available for most patients. If available, records may not reflect antigens of interest.
Reticulocyte harvesting	Can be universally applied to all patients. Rapid turnaround-time (hours). Established technique in some reference laboratories.	Strongly dependent on underlying reticulocyte count. Transfused cells may interfere with test. Complex, labour-intensive test, difficult to perform and interpret. Send out test (1–2 days) for most hospitals.
RBC hypotonic lysis	Rapid turnaround-time (hours). Established technique in some reference laboratories.	Applicable to patients with haemoglobin disorders only. Complex, labour-intensive test, difficult to perform and interpret. Send out test (1–2 days) for most hospitals.
Red cell genotyping	Not affected by recent transfusion. Can be universally applied to all patients. Established technique in some reference laboratories.	Usually acceptable turnaround time (within 1 day). Complex, labour-intensive test, difficult to perform and interpret. Send out test (1–2 days) for most hospitals.