血型與輸血前檢驗

Buzzwords → Dx

Diagnostic Concepts

• ABO blood typing: forward (test RBCs against anti-A, anti-B reagents) + reverse (test plasma against A and B reagent RBCs).
• Rh typing: anti-D reagent.
• Antibody screen: indirect Coombs against panel of group O reagent RBCs with known antigens.
• Crossmatch: major (recipient plasma + donor RBC) → ensures no incompatibility.
• Major blood group antigens to know: Rh (D, C, c, E, e), Kell, Duffy (Fy^a, Fy^b — Fy(a-b-) common in Africans, malaria-resistant), Kidd (Jk^a, Jk^b — delayed HTR), MNS, Lewis, P, Lutheran.
• Cold agglutinin (anti-I usually): IgM, room-temp; significant in autoimmune hemolytic anemia.

Workup (Pre-transfusion)

• Type & screen (T&S) for any potential transfusion: ABO, Rh-D, antibody screen.
• Type & crossmatch (T&C) before transfusion: + crossmatch with selected donor unit.
• Antigen-matched RBCs for chronic transfusion (SCD, thalassemia, MDS) — at minimum match for Rh (C/E/D), Kell; ideally also Kidd, Duffy, S/s, MNS.
• Documentation of clinical alloantibody history — antibody titers may decline below detection but can re-emerge with re-exposure (anamnestic response).

Treatment / Management Algorithm

flowchart TD
  A[Blood transfusion needed] --> B{Urgency}
  B -- routine --> C[Type & crossmatch full T&C<br>30-45 min turnaround]
  B -- urgent (within 30 min) --> D[Type-specific uncrossmatched<br>or O Rh-negative if female childbearing<br>or O Rh-positive if male / older female]
  B -- emergent / no time --> E[Group O Rh-negative emergency blood<br>O Rh-positive acceptable in select pts]
  C --> F[Crossmatch confirmed compatible<br>transfuse]
  D --> G[Switch to crossmatched as soon as available]
  E --> G
  F --> H{Adverse reaction?}
  G --> H
  H -- yes --> I[STOP transfusion immediately<br>workup per reaction type<br>see Transfusion_Reactions]
  H -- no --> J[Continue<br>monitor vitals during]
  C --> K{Antibody screen positive?}
  K -- yes --> L[Identify antibody specificity<br>antigen-negative units required<br>consult blood bank<br>extended crossmatch]

Pearls / Pitfalls

• Group O Rh-negative is universal RBC donor. Group AB is universal plasma donor (no anti-A/B). Group AB Rh-positive is universal recipient.
• Females of childbearing age receiving uncrossmatched blood should get Rh-negative to prevent anti-D sensitization (HDFN risk for future pregnancies).
• Daratumumab interferes with type & screen — binds CD38 on reagent RBCs causing panagglutination. Get T&S BEFORE first dose. To work around: DTT-treated panel cells (denatures CD38) or anti-idiotype antibody.
• Rh-immune globulin (RhoGAM) prevents anti-D sensitization in Rh-negative pregnant women exposed to Rh-positive fetal blood (delivery, miscarriage, amnio, trauma); also for incompatible transfusion.
• Kell is the second most clinically significant antigen group after ABO/Rh — anti-Kell can cause severe HDFN.
• Duffy null (Fy(a-b-)) — most West Africans; resistant to Plasmodium vivax malaria; can produce anti-Fy^a or anti-Fy^b after transfusion.
• Kidd antibodies (anti-Jk^a / anti-Jk^b) — classic for delayed hemolytic transfusion reactions (titer drops below detection between exposures, then anamnestic response). Cause severe DHTR with intravascular hemolysis.
• Bombay phenotype (h/h) — lacks H antigen; appears type O on routine but can't accept any normal blood. Need autologous or other Bombay donors.
• Acquired loss of A or B antigen in leukemia — can resemble type change; crossmatch confirms.
• Cold agglutinins — pre-transfusion, warm incubation may be needed to demonstrate compatibility.
• Anti-K alloimmunization is common in chronic transfusion (esp. SCD); always K-match RBCs for SCD and thalassemia.
• Massive transfusion protocol — 1:1:1 (RBC:plasma:platelet) ratio for trauma; uncrossmatched O-negative initially; switch to crossmatched ASAP.

Cross-references

• Transfusion Reactions
• Blood Products
• Alloimmunization
• MM + daratumumab T&S interference
• SCD chronic transfusion + antigen matching
• Lab Values — DAT, IAT

相關題目

• Q-160 — Universal donor for emergency RBC transfusion
• Q-161 — Anti-D prophylaxis (RhoGAM)
• Q-162 — Bombay phenotype (h/h)

Sources