Final answer:
Blood for cold agglutinins is typically collected in a red-top or pre-warmed lavender-top tube. Agglutination with both anti-A and anti-B antibodies indicates an AB blood type. A cross-match assay is used to check blood compatibility before transfusion.
Step-by-step explanation:
The color tube typically used for collecting blood for cold agglutinins is a red-top tube or sometimes a pre-warmed lavender-top (EDTA) tube. For the blood type testing scenario provided, if a patient's blood agglutinates with both anti-A and anti-B antibodies, this indicates that the patient's blood type is AB, which is a normal response and not an error. Blood type AB means that the erythrocytes contain both A and B antigens.
A cross-match assay is performed to ensure compatibility between donor and recipient blood prior to a blood transfusion. It involves mixing a small sample of donor red blood cells with the serum of the recipient. If hemaglutination occurs, it indicates the presence of antibodies in the recipient's blood against the donor's blood, suggesting an incompatibility. The Coombs' reagent may be added to potentially visualize the interaction of antibodies with red blood cells more clearly.