Given a heterophile antibody titer of 224, which of the following results indicate an error in testing?

A heterophile antibody titer of 224 is indicative of a significant presence of these antibodies, which are often associated with infectious mononucleosis, typically caused by Epstein-Barr virus (EBV). In this context, the term "titer reduction" refers to the dilution series that should show a decrease in the antibody concentration as the dilution increases.

When interpreting titers, a normal procedure is expected to manifest a reduction in titer upon dilution. If there is no titer reduction observed with further dilution (as represented in option B), this suggests that the initial titer could have resulted from factors unrelated to a genuine infection, such as technical artifact, non-specific reactions, or sample handling errors.

One would typically expect titer reductions to occur at subsequent dilutions, particularly beyond the first few. Lack of reduction indicates that the result is not consistent with proper serological behavior, suggesting a possible error in testing or interpretation.

Thus, the scenario where no titer reduction occurs at different dilutions is indicative of a testing error, affirming that option B accurately captures this anomaly in the testing results.