Serology
| Strength Scale | Grade | Value | Appearance of reaction |
| 4+ | Complete | 12 | A single agglutinate. No free cells detected. |
| 3 1/2+ | 4+w or 3+s | 11 | |
| 3+ | 3+ | 10 | Strong reaction. A number of large agglutinates. |
| 2-1/2+ | 3+w or 2+s | 9 | |
| 2+ | 2+ | 8 | Large agglutinates in a sea of smaller clumps, no free cells. |
| 2+w | 2+w | 7 | |
| 1-1/2 | 1+s | 6 | Many medium and small agglutinates and a background of free cells |
| 1+ | 1+ | 5 | Many small agglutinates and a background of free cells |
| 1+w | 1+w | 4 | Many very small agglutinates; with many free cells |
| �+ or - | +/ macro | 3 | Weak granularity in cell suspension. A few macroscopic agglutinatesbut numerous agglutinates microscopically |
| Trace or micro | (+) macro | 2 | Appears negative macroscopically. A few agglutinates of 6-8 cells inmost fields |
| Questionable or micro | 0 | 1 | Rare agglutinates observed microscopically |
| 0 | 0 | 0 | An even cell suspension. No agglutinates observed microscopically. |
Attribution
INTERPRETATION OF AGGLUTINATION REACTIONS. S-STRONG, W-WEAK. (SOURCE: AABB TECHNICAL MANUAL, 10TH EDITION. AMERICAN ASSOCIATION OF BLOOD BANKS, 1117 NORTH 19TH ST. STE 600 ARLINGTON VA, 22209)
