Which test is useful in resolving ambiguity in ABO typing?

Gel testing is considered beneficial for resolving ambiguity in ABO typing due to its high sensitivity and specificity. In this technique, blood samples are mixed with antisera against different ABO antigens in a gel medium. The results can be easily interpreted based on the agglutination patterns, which are visually distinct and occur in a controlled environment that minimizes interference from other factors.

Compared to other methods, gel testing provides a clear and definitive outcome, making it easier to identify discrepancies in ABO group assignments. This is particularly useful in cases where results from more traditional methods may be inconclusive due to weak reactions or technical errors in interpretation. The gel system also allows for the integration of additional tests, such as direct antiglobulin tests or other compatibility assessments, facilitating comprehensive evaluations.

Other methods, while valuable, may not offer the same level of clarity or might be subject to interpretation challenges. For instance, the card method may have limitations in clarity, microscopic analysis may depend heavily on the technician's skill and experience, and digital crossmatching is primarily designed for compatibility testing rather than resolving typing discrepancies. Thus, gel testing stands out as a robust option for clarifying ABO typing results.