Cold agglutinins are autoantibodies (usually IgM) that react optimally at temperatures below 37°C, often at 4°C. Their presence can significantly interfere with ABO reverse grouping, which is often performed at room temperature. Cold agglutinins typically have specificity for the 'I' or 'i' antigens, which are present on all adult (I) or cord (i) red cells. During reverse grouping, the patient's serum is mixed with reagent A1 and B cells. If cold agglutinins are present in high titer, they can cause agglutination of both A1 and B cells, because both cell types express the I antigen. This can mask the true ABO antibodies, leading to discrepant or uninterpretable results (e.g., serum agglutinates both cells strongly, mimicking type O, even if the patient is type A, B, or AB). To resolve this, the reverse grouping should be repeated using a pre-warmed technique (warming serum and cells to 37°C before mixing) to inactivate the cold agglutinins and reveal the true ABO antibodies.

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Zambia

• Joseph Soko – 101 pts

• Visual Pathway Lesions
• Positive and Negative Symptoms
• Hallucinations and Delusions
• Antipsychotic Medications
• Emergency: Environmental Emergencies