Dealing with a clinically important anti-M case with cross-reactivity induced by monoclonal typing reagent

Introduction: The naturally occurring "Anti-M" antibody, which is usually active at temperatures below 37 °C and has no clinical significance, can lead to discrepancy in ABO blood grouping and confusion in diagnosis. Case Presentation: This paper reports the case of a 28-year-old woman whose unanticipated reaction in her reverse blood grouping was observed due to the presence of anti-M, which made interpretation of her blood group difficult. The reason for this discrepancy created an interesting case to analyze. Take-away Lesson: A laboratory should always choose the reagent that is most suitable to the profiles of patients referred to that laboratory. It should be noted that if an anti-M is found in an M+ patient with negative autocontrol, it is not correct to conclude that there is a "partial M".