OD ratio < .90 indicates no detectable Rubella, IgM antibody.
OD ratio 0.91 - 1.09 are equivocal for Rubella, IgM antibody. Suggest a new specimen be collected and re-tested.
OD ratio > 1.10 is positive for Rubella, IgM antibody. A positive value indicates a primary or reactivated infection.