Objective:

To investigate the risk of allergic transfusion reactions (ATRs) in patients with blood type O receiving B or AB plasma or platelets compared to those receiving O products, particularly in regions with high alpha-gal syndrome (AGS) prevalence.

Approach:

• Study Design: International, multicenter, retrospective cohort study of platelet and plasma transfusions from 2020 to 2024 across 40 sites in the US, Australia, Japan, Germany, and France.
• Data Collection: Analysis of 558,823 transfusions with a focus on ATR rates among blood type O patients receiving different ABO products.
• Risk Assessment: Comparison of ATR rates in high vs low AGS prevalence clusters, examining reaction severity and ABO group of transfused products.

Key Findings:

• Patients with blood type O receiving B or AB products had 3.93 times the risk of ATRs compared to those receiving O products in high AGS prevalence areas.
• In low AGS prevalence areas, no excess ATRs were detected for B or AB products.
• B products were associated with 4.48 times the risk of ATRs and AB products with 2.53 times the risk in high AGS prevalence clusters.
• Moderate to severe ATRs were significantly higher in high AGS prevalence areas, with a risk of 9.14 times for B products.

Interpretation:

The study provides epidemiologic evidence suggesting that B antigen-containing products may pose a transfusion risk in regions with high AGS prevalence.

Limitations:

• Retrospective design limited the ability to confirm AGS as the cause of observed reactions.
• Potential underreporting of ATRs due to reliance on passive clinician reporting.
• Geographic misclassification and other unrelated factors could have influenced findings.

Conclusion:

The findings indicate a need for hospitals in high AGS prevalence regions to evaluate local reaction patterns regarding B antigen-containing products.

Sources:

• JAMA Internal Medicine