A zone of red cell lysis (clearing) around the sera on the 'Test' plate significantly larger than any corresponding zone on the 'Control' plate indicates the presence of rubella antibody. Visual comparison of the diameter of the clear zones on the 'Test' plate is adequate for screening purposes:
| Observed: | Result: |
|---|---|
| 'Test' zone larger than +ve control serum and that on 'Control' plate | Rubella antibody present at >5units/ml (concentration of +ve control serum). |
| 'Test' zone smaller than +ve control serum but larger than zone on the 'Control' plate | Low concentration of rubella antibody present (<5 units/ml). |
| 'Test' zone equal to or smaller than zone on 'Control' plate or absent | No rubella antibody detected. |