What if the same packed red blood cells (PRBCs) consistently show a +1 major incompatibility reaction in crossmatching with different patients?

When the Same PRBC Unit Shows +1 Major Incompatibility Across Multiple Different Patients

The blood unit itself likely contains an unexpected antibody or antigen causing the incompatibility and should be quarantined immediately and returned to the blood bank for investigation—this unit should not be transfused to any patient. 1

Immediate Actions Required

Quarantine and Investigation Protocol

• Stop issuing this specific unit immediately and notify the blood bank supervisor that the same donor unit is showing incompatibility with multiple unrelated recipients 1
• The blood bank must investigate the donor unit for:
  • Presence of unexpected antibodies in the donor plasma (particularly relevant if this is whole blood or red cells with significant plasma volume) 2
  • Unusual red cell antigens that may be reacting with common antibodies in the general population 2, 3
  • ABO subgroup variants or weak antigens that could cause discrepant reactions 1
  • Contamination or technical issues with the unit itself 1

Blood Bank Technical Review

• Verify the donor's original blood type and repeat ABO/Rh typing on the unit in question 1
• Perform a direct antiglobulin test (DAT) on the donor unit to detect antibody coating of the red cells 2
• Screen the donor unit for unexpected antibodies using antibody screening cells 2, 3
• Extended phenotyping of the donor unit should be performed to identify rare antigens (Rh system variants, Kell, Kidd, Duffy) that might explain pan-incompatibility 2

Understanding the +1 Incompatibility Pattern

Most Likely Causes

• Donor unit contains an unexpected antibody in residual plasma that is reacting with recipient red cells during the major crossmatch—this is the most common explanation when one unit is incompatible with multiple recipients 2, 3
• The donor may have a rare red cell phenotype with an antigen that many patients in your population have antibodies against (though this would typically show up in the donor screening process) 2
• Technical error in labeling or processing of this specific unit cannot be excluded 1

Why This Matters Clinically

• A +1 reaction indicates weak incompatibility but should never be ignored—even weak incompatibilities can cause hemolytic transfusion reactions, particularly acute reactions if the antibody is IgM or complement-fixing 3
• The fact that this pattern repeats across different patients strongly suggests the problem is with the donor unit, not the recipients 2

Management Decision Algorithm

For the Implicated Unit

1. Do not transfuse this unit to any patient regardless of clinical urgency 1
2. Return the unit to the blood supplier/blood center for investigation and potential donor deferral 1
3. Document the lot number, donation identification number, and all crossmatch results showing incompatibility 1

For Patients Who Need Transfusion

• Select alternative donor units that are fully compatible on major crossmatch 1
• Standard crossmatching with other units should proceed normally—the incompatibility is specific to this one donor unit 1
• If the clinical situation is life-threatening and no compatible blood is available (unrelated to this specific unit issue), follow emergency transfusion protocols with group O Rh-negative blood 1, 4

Critical Pitfalls to Avoid

• Never transfuse a unit showing repeated incompatibility with multiple patients, even if the reaction grade is weak (+1)—this represents a systematic problem with that specific unit 1, 3
• Do not assume the incompatibility is clinically insignificant based on reaction strength alone—antibodies causing +1 reactions can still mediate hemolysis, particularly anti-Jka, anti-C, anti-c, and anti-K 3
• Ensure traceability requirements are met—document the fate of this unit and why it was not transfused, as this is a statutory requirement 1
• Do not delay notifying the blood supplier, as this donor may need to be deferred from future donations if they have developed an unexpected antibody 1

Follow-Up Actions

• The blood bank should communicate findings back to the blood supplier/donor center so appropriate donor counseling and potential deferral can occur 1
• Review your institution's quality management system to ensure this pattern was detected promptly 1
• If multiple units from the same donation session or donor pool are affected, expand the investigation to other units from that collection 1