| Features | Variable | IgM+ n (%) | IgM− n (%) | P-value |
| Gender | Male | 806 (86.1) | 1391 (86.2) | 0.52 |
| Female | 131 (13.9) | 225 (13.8) | ||
| Age | 18 - 30 | 525 (56) | 645 (50.8) | 0.67 |
| 31 - 45 | 332 (38.7) | 784 (43.7) | 0.45 | |
| 46 - 60 | 80 (5.3) | 187 (5.5) | ||
| Profession | Pupil/Student | 157 (14.8) | 266 (15.9) | 0.61 |
| Officials | 136 (9.3) | 146 (4.5) | 0.06 | |
| Unemployed | 207 (27.7) | 513 (30.7) | 0.62 | |
| Worker | 417 (46.9) | 669 (46.9) | 0.47 | |
| Health workers | 20 (1.3) | 22 (2.0) | ||
| Type of donation | Family | 559 (59.6) | 973 (60.2) | 1 |
| Volunteers | 310 (33.1) | 536 (33.2) | 0.2 | |
| Regular | 68 (7.3) | 107 (6.6) | ||
| Blood type | O | 519 (55.4) | 848 (52.5) | 0.85 |
| A | 180 (19.2) | 397 (24.6) | 0.85 | |
| B | 194 (20.7) | 325 (20.1) | 0.73 | |
| AB | 44 (4.7) | 46 (2.8) |