Ways to Minimize Variables

1. technologist: experienced with proven technique

2. red cells: ideally when titres of samples are to be compared, use fresh red cells (antigens deteriorate on storage) from the same donor (same number of antigenic sites present). If this is not possible, use commercial red cells of the same apparent genotype.

3. method: when sequential samples are examined for change in titre, store samples frozen and run new samples in parallel with the immediately preceding sample. This is the most practical way to control that an increase in titre is real.

Ways to Minimize Variables