Distribution of ABO groups and D antigen status
| ABO blood groups | Total (N=5076) | Negative (N=428) | Positive (N=4648) |
| A | 1473 (29.0)* | 141 (9.6) | 1332 (90.4) |
| B | 772 (15.2)* | 48 (6.2) | 724 (93.8) |
| AB | 182 (3.6)* | 18 (9.9) | 164 (90.1) |
| O | 2649 (52.2)* | 221 (8.4) | 2428 (91.7) |
Data presented as N (%).
*Proportion of the total 5076 study population.