PA21.1-6 | Blood Grouping, Crossmatch & Autologous Transfusion — Summary & Reflection

REFLECT

Consider the following scenario and think it through before reading on:

A 45-year-old male patient is admitted for elective colectomy. The surgeon requests a type-and-screen. The blood bank performs forward grouping and gets: Anti-A positive (2+), Anti-B negative. Reverse grouping: A cells positive (1+), B cells negative. How would you interpret this result, and what is the next step?

Reflection guide: Forward grouping suggests group A (Anti-A positive). But reverse grouping also shows A cells positive — which contradicts Landsteiner's rule (a group A patient should have anti-B but no anti-A). This is a grouping discrepancy. Consider: could this be a subgroup of A (e.g., A2 with weak anti-A1)? Could it be a cold agglutinin? Could it be rouleaux? The correct action is to halt, investigate the discrepancy, and use O Rh-negative blood in an emergency while the investigation proceeds.

KEY TAKEAWAYS

Blood Grouping & Crossmatching — Key Points:

• Forward grouping: patient RBCs + anti-A/anti-B/anti-D sera. Reverse grouping: patient serum + A and B reagent cells. Both must agree — discrepancy halts the workflow.

• Methods: slide (quick, low reliability) → tube (traditional gold standard) → gel-card (modern, graded, permanent record). Know all three.

• Agglutination grading: 4+ (solid clump) to 0; gel-card traps agglutinates in column.

• Weak D: D-antigen present at low density; Du test required on donors; label weak-D donors as Rh-positive.

• Discrepancy causes: rouleaux (saline replacement), cold agglutinins (37°C test), clerical error, missing ABO antibodies (neonates).

• Major crossmatch = donor RBCs + recipient serum — the critical safety test. Minor crossmatch = donor serum + recipient RBCs.

• Crossmatch phases: immediate-spin (detects ABO/IgM) → AHG/indirect Coombs phase (detects warm IgG alloantibodies). Check cells MUST be positive after every negative AHG test.

• Electronic crossmatch: only when two concordant ABO typings + negative antibody screen; laboratory must validate.

• Autologous transfusion types: PAD (pre-operative deposit) | ANH (acute normovolaemic haemodilution) | ICS (intraoperative cell salvage).

• Autologous advantages: no alloimmunisation, no TTI, no haemolytic reactions, no TRIM. Contraindications/limitations: contaminated field (bowel surgery for ICS), malignancy (controversial), anaemia (PAD), cardiovascular instability (ANH).