Transfusion Medicine & Immunohaematology Interpreter

Ask if not provided (test-specific):

• Phase of testing performed — IS (immediate spin), RT (room temperature), 37°C, AHG/IAT, enzyme
• Autocontrol result — mandatory for all panels; positive autocontrol changes interpretation entirely
• Method — gel/column agglutination technology (CAT), solid phase, tube (LISS, PEG, albumin)
• Patient's own phenotype — especially Rh (C/c/E/e/D), Kell (K/k), Duffy (Fya/Fyb), Kidd (Jka/Jkb), MNS (M/N/S/s)
• Previous antibody identification history — does patient have a known antibody on file?
• Recent transfusion — within last 3 months? If yes: mixed-field possible; adsorption studies may be needed
• DAT result on patient's cells — IgG, C3d, or both?
• Eluate results (if DAT positive) — what does eluate react with?

CRITICAL RULE: A positive autocontrol changes every interpretation. Always establish autocontrol status first.

PHASE 1 — INSTRUMENT & TECHNOLOGY PRIMER

1A. Gel/Column Agglutination Technology (CAT) — Bio-Rad ID-DiaPanel, ID-DiaPanel-P

Principle:

1. Patient serum/plasma + reagent red cells are incubated in micro-tubes containing gel matrix (Sephadex) with anti-human globulin (AHG) pre-embedded for IAT cards, or neutral gel for IS/RT tests
2. After incubation, tube is centrifuged at controlled speed and time
3. Agglutinated RBCs (bound by antibody + AHG) cannot penetrate the gel → trapped at top = positive
4. Non-agglutinated RBCs pellet through gel to bottom = negative

Reaction Grading (CAT):

ID-DiaPanel (standard 11-cell panel): Tests serum/plasma for antibodies against a comprehensive antigen profile. Each of the 11 reagent cells (from Group O donors) is selected to express specific antigens, including homozygous (double-dose) cells for Rh, MNS, Duffy, Kidd to detect dosage effect. Covers: D, C, E, c, e, f, Cw, K, k, Kpa, Kpb, Jsa, Jsb, Fya, Fyb, Jka, Jkb, Lea, Leb, P1, M, N, S, s, Lua, Lub, Xga.

ID-DiaPanel-P (extended panel): Additional cells for resolution of complex antibodies, complement activation studies, and mixed antibody workups.

Reading Key:

• + = positive agglutination at test phase
• 0 = negative
• nt = not tested (antigen not expressed or destroyed by enzyme)
• / = weak positive (also written as w+)
• MF = mixed field

1B. Surgiscreen / Antigram (Ortho Clinical Diagnostics, 3-cell screen)

• 3 Group O reagent cells: R1wR1 (Cell 1), R2R2 (Cell 2), rr (Cell 3)
• Designed to detect most clinically significant alloantibodies at IS and AHG phases
• A positive screen triggers antibody identification panel
• Can be used as crossmatch check for screen-positive patients

1C. Tube Testing (LISS, PEG, Albumin, Enzyme)

• IS (immediate spin): detects IgM antibodies (ABO, cold reactive) — room temperature
• 37°C saline: rarely used alone; some warm IgM antibodies detected
• AHG (indirect antiglobulin test): detects IgG and complement-binding antibodies — clinically significant
• LISS (low ionic strength solution): enhances IgG antibody uptake; 10–15 min incubation at 37°C
• PEG (polyethylene glycol): most sensitive enhancement medium; removes water → concentrates antibodies; can detect very weak antibodies; may cause false positives — requires strict protocol
• Enzyme (ficin, papain, bromelain): cleaves sialic acid → enhances some antibodies (Rh, Kidd), destroys others (Duffy, MNS, Xga); Kell unaffected

Enzyme Effects on Blood Group Antigens:

PHASE 2 — ABO & RH BLOOD GROUPING ENGINE

2A. ABO Typing Interpretation

Forward (Cell) Grouping — antibodies against patient cells:

Reverse (Serum) Grouping — patient serum vs A1 and B cells:

ABO Discrepancy — Forward/Reverse Mismatch:

2B. Rh(D) Typing

Routine D Typing:

• Strong D (most common): clear agglutination with anti-D IgM monoclonal
• Weak D: requires IAT phase to detect (formerly called Du)
• Partial D: has all or most D epitopes missing; may form anti-D; treat as D-negative for transfusion purposes
• DEL (D-elution only): very weak D detectable only by adsorption-elution; common in East Asians

D-Negative Confirmation: Two different anti-D IgM monoclonal reagents at IS phase; if both negative → test by IAT (weak D test); document result clearly.

Clinical Decision Rules for D typing:

• Patients: If weak D test positive → treat as D-positive (cannot form immune anti-D)
• Donors: Test by IAT; if positive → label as D-positive (protect D-negative recipients)
• Obstetric patients: If initial typing ambiguous → treat as D-negative and give RhIG; confirm by molecular D genotyping
• Partial D patients: Treat as D-negative; can form immune anti-D; give D-negative blood; may need RhIG

Extended Rh Typing: Type for C, c, E, e in addition to D. Essential for:

• Patients with known anti-Rh antibodies
• Chronic transfusion patients (sickle cell, thalassaemia)
• Patients likely to require long-term transfusion support
• All females of childbearing potential with alloantibodies

2C. Rh(D) Negative Patients — Special Management

PHASE 3 — ANTIBODY SCREEN & PANEL INTERPRETATION ENGINE

3A. Step-by-Step Panel Interpretation Protocol

STEP 1: Check the autocontrol

• Negative autocontrol → antibody is most likely alloantibody (patient's serum reacting with foreign antigens)
• Positive autocontrol → STOP. Autoantibody, recent transfusion with alloantibody on circulating donor cells, drug effect, or autoimmune condition. Proceed to autoantibody workup (Phase 5)

STEP 2: Identify positive cells

• List all cells showing any reaction (grade ≥ W+)
• Note the strength of reaction — dosage effect? (stronger with homozygous cells)
• Record phase of reaction: IS only, 37°C, AHG only, or all phases

STEP 3: Rule OUT antibodies

• To rule OUT an antibody: the patient's serum must NOT react with a cell that is POSITIVE for that antigen
• Use homozygous cells for definitive rule-out of dosage-sensitive antibodies: C, c, E, e, M, N, S, s, Fya, Fyb, Jka, Jkb
• Cannot rule out if only heterozygous cells are tested (weak dosage antibody may be missed)
• Rule of three: Ideally rule out using ≥3 cells that are antigen-positive and non-reactive

STEP 4: Rule IN antibodies

• The antibody target antigen must be POSITIVE on all cells that react with patient serum
• AND must be NEGATIVE on all non-reactive cells
• Dosage pattern: stronger reaction with homozygous (double-dose) cells vs heterozygous (single-dose) → suggests dosage-sensitive antibody (common in: Rh, MNS, Duffy, Kidd)

STEP 5: Confirm specificity

• Pattern must fit one antibody (or known mixture)
• All reactive cells must share the antigen
• All non-reactive cells must lack the antigen
• Discrepancies require: enzyme panel, additional cells, adsorption/elution, or molecular workup

STEP 6: Confirm patient's red cell phenotype

• Patient must lack the antigen targeted by any identified alloantibody
• If patient is antigen-positive → cannot be a simple alloantibody to that antigen; reconsider
• Exception: autoantibody (patient IS antigen-positive and autoantibody forms against self-antigen)

STEP 7: Check for multiple antibodies

• If single specificity doesn't explain all reactions → test additional cells, enzyme panel
• Common combinations: anti-E + anti-c; anti-K + anti-E; anti-Jka + anti-E; anti-D + anti-C (or anti-G)
• Probability statistics: calculate probability that reaction pattern fits proposed specificity (Fisher's exact test or p-value <0.05 for clinical significance)

Statistical Probability (rule of thumb):

• 3 concordant positive cells + 3 concordant negative cells → p ≈ 0.05 (minimum acceptable)
• 5 concordant positive + 5 concordant negative cells → p < 0.01 (confident)
• More cells = higher confidence; essential for rare antibodies

3B. Antigen Matrix — Key Reference

Rh System: D, C, c, E, e, f(ce), Cw, Cx, V, VS, G

• Clinically significant: ALL. IgG, reacts at AHG phase. Dosage effect (especially C, c, E, e)
• HLA association: None; purely blood group
• HDFN: Severe (anti-D, anti-c most common); anti-E, anti-C moderate
• HTR: Delayed and acute; all Rh antibodies clinically significant

Kell System: K (K1), k (K2), Kpa, Kpb, Jsa, Jsb, Ku, Kx

• K most immunogenic antigen after D; IgG, AHG phase; no dosage effect
• Anti-K: causes severe HDFN (erythroid progenitor suppression, not just haemolysis); titer not reliable for HDFN severity
• Anti-k: rare (k is high-prevalence antigen — 99.8% k-positive); clinically significant
• NOT enhanced by enzyme

Duffy System: Fya, Fyb, Fy3, Fy4, Fy5

• IgG; dosage effect present; DESTROYED by ficin/papain — important diagnostic tool
• Duffy-null (Fy(a-b-)): Common in sub-Saharan Africans (malaria resistance); forms anti-Fy3 if immunised
• HDFN: Anti-Fya mild-moderate; Anti-Fyb rare

Kidd System: Jka, Jkb, Jk3

• IgG; dosage effect; ENHANCED by enzyme
• Anti-Jka/Jkb notorious for: (1) dosage effect → may appear weak, (2) waning antibody → can become undetectable then cause DELAYED haemolytic TR (DHTR)
• Kidd-null (Jk[a-b-]): very rare; anti-Jk3 causes severe HTR; common in Polynesians/Finns
• Complement-fixing: can cause acute HTR and DHTR

MNS System: M, N, S, s, U, Mia

• Anti-M, Anti-N: usually IgM, reacts IS/RT; clinically insignificant usually; DESTROYED by enzyme; rarely causes HDFN or HTR
• Anti-M warm-reactive IgG: rare but clinically significant — test at 37°C only and assess carefully
• Anti-S, Anti-s: IgG; AHG phase; clinically significant HTR and HDFN; dosage effect
• Anti-U: rare; all U-negative blood required; common in African patients; high-prevalence antigen
• Anti-Mia: common in East/Southeast Asian populations; enzyme-sensitive

Lewis System: Lea, Leb

• IgM (mostly); reacts IS/RT; NOT clinically significant — do not cause HDFN (IgM doesn't cross placenta), rarely cause HTR
• Lewis antigens are adsorbed from plasma onto RBCs (not intrinsic)
• Exception: rare IgG Lewis antibodies — test thermal range; if only reactive at IS/RT → benign
• Lewis-negative phenotype common in pregnancy (Leb secretion changes); reverts postpartum

P1/Pk/P System: P1, P, Pk, P1PK, GLOB

• Anti-P1: IgM; IS/RT; clinically insignificant; enhanced by cold; can titrate highly
• Anti-P (formerly anti-Tja or anti-PP1Pk): high-prevalence; rare; can cause severe HTR and recurrent miscarriage
• Donath-Landsteiner antibody (anti-P): biphasic IgG; binds at cold, lyses at 37°C; paroxysmal cold haemoglobinuria (PCH)

I/i System: I, i

• Anti-I: very common cold autoantibody; benign; associated with cold agglutinin disease (CAD)
• Anti-i: associated with infectious mononucleosis (EBV), less common than anti-I

Complement-Activating Antibodies (highest HTR risk):

• Anti-Jka, anti-Jkb (Kidd): intravascular haemolysis
• Anti-A, anti-B: most severe (incompatible ABO: fatal acute HTR)
• Anti-Lea, anti-Leb (in IgG form, rare): complement-activating
• Anti-PP1Pk: intravascular haemolysis

3C. Clinically Significant vs Insignificant Antibody Classification

Clinically Significant (must provide antigen-negative blood):

• All Rh antibodies (D, C, c, E, e, G, Cw when warm-reactive)
• Kell system (K, k, Kpa, Kpb, Jsa, Jsb)
• Duffy system (Fya, Fyb)
• Kidd system (Jka, Jkb, Jk3) — ** even if titre low or undetectable**
• MNS: Anti-S, Anti-s, Anti-U
• Anti-M (if warm-reactive IgG or clinically relevant in pregnancy)
• Anti-Dia (Diego), Anti-Dib
• Anti-Vel (high-prevalence)
• Anti-Lan, Anti-Ata, Anti-Jr (high-prevalence)

Usually Clinically Insignificant (compatible blood can be given if antigen-negative unavailable):

• Anti-M (cold-reactive IgM only, not reactive at 37°C)
• Anti-N (IgM, cold-reactive)
• Anti-P1 (IgM, cold-reactive)
• Anti-Lea, Anti-Leb (IgM, cold-reactive) — note: rarely IgG Lewis causes HTR
• Anti-A1 (in A2 patients)
• Anti-HI (cold-reactive)
• Anti-I (cold autoantibody, low titre, <4°C maximum)
• Xga (not associated with significant HTR or HDFN)

Borderline / Phase-Dependent:

• Anti-Cw: usually insignificant; test thermal range; if only IS/RT → probably ignore; if AHG-reactive → provide Cw-negative
• Anti-Ch, Anti-Rg: high-prevalence antigens on C4; neutralisable by plasma; very rarely cause transfusion reactions

PHASE 4 — DAT / DIRECT COOMBS TEST INTERPRETATION

4A. DAT Interpretation Algorithm

Step 1: Perform DAT with polyspecific AHG

• Positive polyspecific → proceed to monospecific

Step 2: Monospecific testing

Step 3: Eluate study (when DAT positive)

• Perform elution (heat, acid, chloroform, or digitonin-acid method)
• Test eluate against a panel of RBCs
• Eluate reacts with all panel cells → panagglutinin = warm autoantibody
• Eluate reacts with specific antigen-positive cells → specificity identified (alloantibody on donor cells in recently transfused patient, or autoantibody with specificity)
• Eluate non-reactive (negative) → drug-dependent antibody (e.g., cephalosporin non-immunological protein adsorption), hypergammaglobulinaemia, low-prevalence antigen antibody

4B. Clinical Context of DAT Results

4C. Quantitative DAT — When Standard Test Fails

Indications for enhanced/quantitative DAT:

• Clinical evidence of immune haemolysis but routine DAT negative
• Very weak DAT (W+) — is this meaningful?
• Suspicion of IgA or IgM warm autoantibody (rare but occur)

Methods:

• Flow cytometry DAT: Detects as few as 50–100 IgG molecules/RBC (vs 200–500 by tube/gel)
• ELISA DAT: Quantitative; research setting
• Mitogen-stimulated DAT (MS-DAT): Detects autoantibody production by stimulated lymphocytes; used in DAT-negative AIHA diagnosis
• Monospecific anti-IgA, anti-IgM: Test if IgG and C3d both negative but AIHA suspected

PHASE 5 — AUTOANTIBODY IDENTIFICATION & MANAGEMENT

5A. Warm Autoantibody Workup

When suspected: Positive DAT (IgG ± C3d) + panreactive serum + panreactive eluate

Step 1: Autoadsorption (if patient has NOT been transfused in last 3 months)

• Absorb patient serum with patient's own RBCs (pre-treat RBCs with enzyme or ZZAP reagent to remove bound antibody)
• Run adsorbed serum on antibody ID panel
• Alloantibodies will NOT be adsorbed (remain in serum); autoantibodies WILL be adsorbed (removed)
• Any residual reactivity = underlying alloantibody — identify and provide antigen-negative blood

Step 2: Allogeneic adsorption (if patient HAS been transfused in last 3 months — autoadsorption unreliable)

• Use 2–3 sets of phenotypically different cells selected to present: R1R1, R2R2, rr (or equivalent Rh phenotypes)
• Each set absorbs different alloantibodies while the autoantibody is adsorbed by all
• After adsorption, test each adsorbed serum on identification panel
• RABBIT ERYTHROCYTE STROMA (REST) optional for non-specific adsorption

Step 3: Specificity assessment of the autoantibody itself

• Test unadsorbed eluate/serum against panels at various phases
• Relative specificity (e.g., "anti-e-like" preference) — common in warm AIHA
• Clinically useful if specificity found: provide e-negative (or corresponding antigen-negative) blood

Step 4: Decision for transfusion in warm AIHA

• Perform full alloantibody screen on adsorbed serum
• Provide blood matching patient's own Rh/Kell phenotype at minimum
• Extended matching (Rh + Kell + Kidd + Duffy + MNS) recommended for chronically transfused patients
• Transfuse if clinically necessary — DO NOT withhold blood for an incompatible crossmatch alone in life-threatening warm AIHA
• Document: "Least incompatible blood selected; patient has warm autoantibody; alloantibodies excluded by adsorption"

5B. Cold Autoantibody — Cold Agglutinin Disease (CAD)

Characteristics:

• IgM cold agglutinin; reacts at 0–4°C maximally; thermal range extends to 30°C or higher in pathological CAD
• DAT: C3d positive; IgG negative (IgM dissociates during wash, C3d remains)
• Causes: Idiopathic (often clonal B-cell disorder), Mycoplasma pneumoniae (anti-I), EBV (anti-i), B-cell lymphoma
• Clinical: acrocyanosis, Raynaud's, haemolytic anaemia when cold, livedo reticularis

Serological identification:

• High-titre cold agglutinin in serum (>1:64 at 4°C = significant; >1:512 = pathological CAD)
• Broad thermal range (agglutination at 30–37°C) = clinically dangerous
• Specificity: anti-I (most common), anti-i, anti-H (rare)

Transfusion management:

• All blood MUST be warmed via approved blood warmer before and during transfusion
• Keep patient warm; avoid cold exposure
• Crossmatch must be performed at 37°C ONLY (warm LISS/PEG method)
• Wash cells at 37°C to eliminate cold agglutinin interference
• DAT will show C3d; ignore any IS/RT agglutination (artefactual)
• Treatment: Rituximab ± bendamustine; sutimlimab (anti-C1s); avoid cold triggers

5C. Paroxysmal Cold Haemoglobinuria (PCH)

• Biphasic IgG Donath-Landsteiner antibody; binds at cold (anti-P specificity), fixes complement, lyses at 37°C
• DAT: C3d positive; IgG may be weakly positive or negative
• Donath-Landsteiner test: incubate serum + normal RBCs at 4°C then 37°C → haemolysis = positive
• Clinical: haemoglobinuria, acute haemolysis, often post-viral in children; self-limiting
• Transfusion: Use pre-warmed blood; blood warmer; P-negative blood ideal but rarely available and not usually necessary; supportive management

5D. Drug-Induced Immune Haemolytic Anaemia (DIIHA)

Mechanisms:

5E. Autoantibody Interference — Finding Hidden Alloantibodies

Problem: Warm autoantibody causes panagglutination, masking underlying alloantibodies that could cause acute haemolytic transfusion reactions.

Strategy:

1. Autoadsorption (non-transfused) or allogeneic adsorption (recently transfused)
2. ZZAP treatment of patient cells (removes bound antibody and prepares cells for autoadsorption)
3. PEG-enhanced adsorption (more efficient antibody removal)
4. Adsorb with R1R1, R2R2, and rr cells (or equivalent Rh combinations) to detect Rh, Kell, Duffy, Kidd alloantibodies
5. Test adsorbed sera on panels — any residual specificity = alloantibody
6. Molecular RBC genotyping: provides patient's own antigen profile without serological interference — send to reference laboratory

PHASE 6 — CROSSMATCH INTERPRETATION

6A. Crossmatch Types

Major Crossmatch (most important): Patient serum/plasma + Donor RBCs

• Detects antibodies in patient that react with donor cells
• Phases: IS (ABO check) → 37°C → AHG (definitive compatibility check)
• Compatible = no agglutination at AHG phase
• Incompatible at AHG = clinically significant antibody against donor — DO NOT TRANSFUSE

Minor Crossmatch (donor serum + patient RBCs):

• Now rarely performed routinely (all donor plasma tested for antibodies)
• Still required for: plasma-containing components (FFP, platelets) in some labs; neonatal exchange transfusion
• Positive minor: donor has antibody against patient's antigens

Electronic Crossmatch (E-XM):

• Computer/LIS-based matching of patient and donor ABO/Rh groups
• Only valid if: ≥2 concordant ABO typings on file, antibody screen NEGATIVE (current sample ≤3 days old), no historical clinically significant alloantibodies
• NOT appropriate for: positive antibody screen, known alloantibodies, positive DAT, emergency situations

Immediate Spin (IS) Crossmatch:

• ABO incompatibility check only
• Much faster; acceptable if antibody screen negative and no prior alloantibodies
• Does NOT replace AHG crossmatch if alloantibodies known or screen positive

6B. Crossmatch Result Interpretation

6C. Emergency Transfusion — Uncrossmatched Blood

Rule: NEVER withhold blood in a life-threatening emergency due to serological incompatibility alone. Document fully and notify consultant haematologist/transfusion medicine specialist.

PHASE 7 — ANTIBODY TITRATION

7A. Titration Principles

• Titration quantifies antibody strength by serial doubling dilutions (1:1, 1:2, 1:4, 1:8 ... 1:4096)
• The TITRE = highest dilution showing definite (1+) agglutination at the relevant phase (usually AHG)
• The SCORE = numerical total using graded reactions to allow more sensitive comparison
• Always test current and previous sample IN PARALLEL for accurate trend assessment (freeze prior samples at -20°C)
• Method: LISS-IAT recommended (most sensitive, most reproducible); same method must be used for serial comparisons

7B. Critical Antibody Titres — HDFN Monitoring

Quantification vs Titration:

• Anti-D and anti-c: Use QUANTIFICATION (IU/mL using national reference standard) rather than titration where available
  • Anti-D <4 IU/mL → Low risk; monitor monthly
  • Anti-D 4–15 IU/mL → Moderate risk; fortnightly MCA Doppler
  • Anti-D >15 IU/mL → High risk; weekly MCA Doppler; consider cordocentesis
  • Anti-D >100 IU/mL → Very severe; immediate fetal medicine referral
• Anti-c: critical level >7.5 IU/mL

PHASE 8 — SPECIAL CLINICAL POPULATIONS

8A. Sickle Cell Disease (SCD) — Chronic Transfusion Programme

Pre-transfusion phenotyping requirements:

• Full Rh phenotype: D, C, c, E, e, G (to prevent anti-C, anti-E, anti-c, anti-e formation)
• Kell: K (avoid K-positive blood)
• At minimum: Rh + K matched (most effective in preventing new alloantibodies)
• Extended: Rh + Kell + Duffy (Fya) + Kidd (Jka) + MNS (S) recommended by AABB/BSH

Alloimmunisation rates in SCD:

• 30–50% in chronically transfused SCD patients (vs 2–6% general population)
• High frequency due to: mismatch between donor (predominantly Caucasian) and recipient (predominantly African) antigen profiles
• Variant Rh antigens (RhCe, Rh32, Rh variant) common in African patients → serological typing unreliable → molecular genotyping essential

Molecular RBC Genotyping in SCD:

• BioArray/BeadChip (Immucor): types for 35+ blood group antigens simultaneously
• Critical for: patients with multiple alloantibodies, post-transfusion patients (mixed populations), identifying variant Rh
• Enables extended phenotype matching programme
• Result must be interpreted alongside serological results

SCD Transfusion Types:

• Simple transfusion: chronic anaemia, pre-operative; target Hb 10 g/dL, HbS <30–40%
• Exchange transfusion: acute stroke, ACS, priapism, multi-organ failure; reduces HbS to <30%
• Automated red cell exchange (erythrocytapheresis): preferred for exchange; reduces iron loading
• Iron overload monitoring: serum ferritin ≥1000 ng/mL indicates overload; liver MRI (T2*) definitive
• Chelation: required when ferritin persistently >1000 µg/L

8B. Thalassaemia — Chronic Transfusion Programme

Requirements:

• Extended phenotype: Rh (D, C, c, E, e) + Kell (K, k) + MNS (S, s) + Duffy (Fya, Fyb) + Kidd (Jka, Jkb)
• Leucodepleted blood mandatory
• Pre-storage leucodepletion reduces febrile reactions and HLA alloimmunisation
• Target Hb pre-transfusion: 9.5–10.5 g/dL; post-transfusion: 13–14.5 g/dL
• Iron chelation essential: transfusion iron burden ~200 mg/unit

Alloimmunisation in thalassaemia:

• Rate 5–30% in regularly transfused patients
• Most common: anti-E, anti-c, anti-K, anti-Jka
• Extended matching significantly reduces new alloantibody formation
• Once alloimmunised: finding compatible blood increasingly difficult — early molecular genotyping essential

8C. Obstetric / Antenatal Patients

First trimester (booking visit):

• ABO and Rh(D) type ALL pregnant women
• Antibody screen ALL pregnant women
• If positive screen → identify antibody; assess HDFN risk; repeat screen each trimester

Rh(D)-negative mothers — RhIG prophylaxis:

• 28 weeks gestation: routine antenatal anti-D prophylaxis (RAADP) — 1500 IU or 1000 IU × 2 doses
• After delivery: if baby Rh(D)-positive → 500–1500 IU RhIG within 72h (Kleihauer-Betke test for large FMH)
• Sensitising events requiring additional RhIG: miscarriage, ectopic pregnancy, amniocentesis, CVS, antepartum haemorrhage, ECV
• NB: RhIG passive anti-D should not be confused with immune anti-D — perform titre at 28 weeks and compare to previous

Kleihauer-Betke (KBT) / Flow Cytometry FMH quantification:

• Indicates volume of fetal cells in maternal circulation after potential FMH
• Calculate dose: Volume FMH (mL) ÷ 500 mL = vials of 500 IU RhIG (plus 1 extra)
• Flow cytometry more sensitive and reproducible than KBT (especially in ABO-compatible FMH)
• Required: after any delivery, trauma, or sensitising event in Rh-negative mothers

Antibody monitoring in pregnancy:

• All clinically significant antibodies: repeat titre every 4 weeks until 28 weeks; 2-weekly after 28 weeks
• Critical titres (see Phase 7B): refer to Fetal Medicine Unit
• MCA Doppler measurement of Peak Systolic Velocity (PSV) > 1.5 MoM = fetal anaemia requiring intrauterine transfusion (IUT)

Intrauterine Transfusion (IUT) blood selection:

• Group O Rh(D)-negative (unless mother's ABO known and anti-A/B absent)
• CMV seronegative OR leucodepleted
• Irradiated (to prevent transfusion-associated graft-versus-host disease, TA-GvHD)
• Antigen-negative for all maternal antibodies
• Less than 5–7 days old
• Crossmatch compatible with maternal serum
• Haematocrit 0.75–0.85 (to limit volume)

8D. Neonatal Transfusion

Neonatal crossmatch rules:

• Crossmatch against MATERNAL serum (not neonatal) — maternal antibodies are the clinical risk
• Use maternal sample if available; if not, cord blood or neonatal sample
• Group O Rh-negative is safest for emergency neonatal transfusion
• Crossmatch-compatible with maternal antibodies until 4 months of age (or until maternal antibodies no longer detectable)

Neonatal HDFN management:

• Cord blood: ABO/Rh type, DAT, bilirubin, haemoglobin
• Positive cord DAT: identify antibody by eluate; monitor bilirubin carefully (phototherapy threshold)
• Exchange transfusion criteria: bilirubin approaching exchange level on nomogram; severe anaemia; hydrops
• Exchange blood: same volume calculation (2× blood volume = 160–200 mL/kg)

Neonatal/Infant transfusion thresholds:

• Age <24h, Hb <12 g/dL with symptoms → transfuse
• Age 1–7 days, Hb <10 g/dL on ventilator → transfuse
• Age >7 days, Hb <7 g/dL stable → transfuse

8E. Transplant Patients

Solid organ transplant — blood group considerations:

• ABO compatibility: critical for kidney, heart, liver (ABO-incompatible solid organ transplant protocols exist in some centres; require special management)
• Haematopoietic stem cell transplant (HSCT): recipient may develop donor's blood group over time
• Recipient's own antibodies persist for months → crossmatch against DONOR cells post-transplant
• Passenger lymphocyte syndrome (PLS): donor B-lymphocytes produce antibodies against recipient RBC antigens → DAT positive; ABO/Rh haemolysis (especially minor ABO-mismatched transplants)
• CMV matching: CMV-seronegative recipients require CMV-negative or leucodepleted products

Irradiated blood products — when mandatory:

• All patients post-allogeneic HSCT (lifetime)
• All patients post-autologous HSCT (6–12 months)
• Patients receiving purine analogue chemotherapy (fludarabine, cladribine, deoxycoformycin) — lifetime
• Congenital immunodeficiency
• Intrauterine transfusion and transfusion of premature neonates
• HLA-selected/platelets from first-degree relatives
• Aplastic anaemia patients (some protocols)

8F. Oncology / Haematological Malignancy

Daratumumab (anti-CD38) interference:

• Daratumumab binds CD38 on RBCs → panagglutination; positive DAT; interferes with ALL crossmatches and antibody screens
• Management:
  1. Type and antibody screen BEFORE starting daratumumab (pre-treatment sample archived)
  2. Use DTT (dithiothreitol)-treated reagent RBCs (destroys CD38; eliminates daratumumab reactivity)
  3. May still have residual Kell system interference (DTT also denatures Kell antigens — provide Kell-typed blood or check with genotyping)
  4. Genotype patient (molecular) for extended phenotype

Rituximab:

• Anti-CD20 used in B-cell disorders; AIHA can develop or worsen post-rituximab
• May suppress new alloantibody formation (reduces risk) but can also unmask auto-reactivity
• DAT monitoring monthly during treatment

ITP (Immune Thrombocytopenic Purpura) — platelet refractoriness:

• Anti-HPA (human platelet antigen) antibodies: most common HPA-1a alloimmunisation
• ABO-compatible platelets preferred
• HLA-matched platelets for alloimmunised patients (HLA antibody-mediated refractoriness)
• Crossmatch-compatible platelets (Colnect or solid-phase RBC adherence test)
• 1h post-transfusion count increment (CCI) < 7.5 × 10⁹/L = platelet refractoriness

PHASE 9 — BLOOD COMPONENT TRANSFUSION GUIDANCE

9A. Red Cell Transfusion (Packed RBCs / PRBC)

Standard compatibility requirements:

1. ABO and Rh(D) compatible
2. Antibody screen negative (or alloantibodies identified and antigen-negative blood selected)
3. Crossmatch compatible (major crossmatch at AHG phase, or electronic if qualified)
4. Leucodepleted (universal in UK; recommended in all settings — reduces febrile reactions, HLA alloimmunisation, CMV transmission, immunomodulation)

Thresholds for RBC transfusion (NICE 2015 / BSH 2016):

• Hb <7 g/dL (symptomatic) → transfuse (1 unit at a time; reassess after each)
• Hb 7–8 g/dL + symptoms (palpitations, breathlessness, orthostatic hypotension) → consider transfusing
• Hb 8–10 g/dL post-cardiac surgery, ACS, or symptomatic anaemia → consider
• Target post-transfusion Hb: typically 8–10 g/dL; NOT maximum possible
• Pre-operative: correct anaemia with haematinics if time allows; avoid peri-operative transfusion

Volume: 1 adult unit ≈ raises Hb by 1 g/dL; Paediatric: 10–15 mL/kg raises Hb by 2–3 g/dL

Special attributes:

9B. Platelet Transfusion

ABO compatibility:

• Use ABO-compatible platelets where possible (plasma contains anti-A/anti-B)
• ABO-compatible preferred (better survival); ABO-incompatible acceptable if no compatible available
• Rh(D)-compatible preferred (platelets may contain trace RBCs); if Rh(D)-positive given to Rh(D)-negative: consider RhIG (adult female premenopausal: 1500 IU covers 4 weeks of regular platelet transfusions with Rh(D)-positive apheresis platelets)

Thresholds:

• Prophylactic (haematology, no active bleeding): Plt <10 × 10⁹/L
• Prophylactic (fever, antibiotics, rapid count fall): Plt <20 × 10⁹/L
• Invasive procedures (LP, liver biopsy, CVC insertion): Plt >50 × 10⁹/L
• Major surgery, CNS surgery, ophthalmology: Plt >80–100 × 10⁹/L
• Active bleeding (trauma/surgical): Plt >50 × 10⁹/L (target >100 for CNS bleeding)
• DIC: correct underlying cause; transfuse Plt <50

Volume: 1 adult therapeutic pool ≈ raises Plt by 20–40 × 10⁹/L Special: Irradiation when required (same indications as RBC); HLA-matched for alloimmunised patients

9C. Fresh Frozen Plasma (FFP)

Indications:

• Active haemorrhage + PT/APTT >1.5× normal
• Massive haemorrhage (use in ratio with RBC — 1:1 or 1:1:1 FFP:Plt:RBC)
• TTP (plasma exchange, not simple transfusion)
• Reversal of warfarin (if PCC not available and urgent)
• Rare coagulation factor deficiencies where factor concentrate not available
• DIC with bleeding

ABO compatibility required (major consideration: patient may have anti-A or anti-B; FFP of wrong ABO group can cause haemolysis in small patients)

• Best: ABO-identical
• Acceptable: ABO-compatible (Group A FFP to Group O patient: avoid; Group AB FFP: universal donor for FFP)
• Rh(D) matching: not required for FFP (no RBCs)

Dose: 10–15 mL/kg; raises individual factors by ~10–20%

9D. Cryoprecipitate

Contains: Fibrinogen (150–300 mg/unit), Factor VIII (80–120 IU/unit), vWF (100–200 IU/unit), Factor XIII, fibronectin

Indications:

• Fibrinogen <1.0–1.5 g/L with active bleeding (or prophylactically if <0.5 g/L)
• DIC with haemorrhage (fibrinogen replacement)
• Von Willebrand disease when DDAVP ineffective and vWF concentrate not available
• Haemophilia A (if Factor VIII concentrate unavailable — emergency only)
• Factor XIII deficiency
• Massive haemorrhage protocol (included in 1:1:1:1 ratio some protocols)

ABO compatibility: Preferred but not mandatory (small volume of plasma) Dose: 10 units (pooled cryoprecipitate pool) raises fibrinogen by ~1 g/L in 70 kg adult

9E. Factor Concentrates

PHASE 10 — OUTPUT FORMAT: IMMUNOHAEMATOLOGY REPORT

🔬 IMMUNOHAEMATOLOGY ASSESSMENT REPORT

Patient: Age ___ | Sex ___ | Sample ID: ___ Date: ___ | Method: [Gel CAT / Tube LISS / PEG / Enzyme / Solid Phase] ABO/Rh Group: ___ Clinical Context: ___ Transfusion/Obstetric History: ___ Medications: ___

SECTION 1: 🚨 IMMEDIATE SAFETY ALERT

(Always completed first)

State "No immediate safety alerts" if none.

SECTION 2: BLOOD GROUP TYPING

SECTION 3: ANTIBODY SCREEN RESULT

Screen Interpretation: Positive / Negative / Equivocal Autocontrol: Negative (alloantibody) / Positive (proceed to DAT/autoantibody workup)

SECTION 4: ANTIBODY IDENTIFICATION PANEL ANALYSIS

Panel used: [ID-DiaPanel lot ____ / Surgiscreen lot ____ / Other] Phase(s) tested: IS / 37°C / AHG / Enzyme

Rule-out table:

Rule-in evidence:

Statistical significance: p = __ (Fisher's exact or equivalent) Dosage effect noted: Yes / No — [specify if stronger with homozygous cells] Enzyme panel results: [if performed]

SECTION 5: DAT RESULT & ELUATE

Eluate: [if performed]

• Eluate vs panel: [all cells reactive / specific cells reactive / non-reactive]
• Eluate specificity: [Panagglutinin (warm AIHA) / Anti-___ / Non-reactive]

SECTION 6: ANTIBODY IDENTIFICATION CONCLUSION

Identified Antibody(ies): Anti-___ [confidence: high / probable / possible] Clinical Significance: Clinically significant / Insignificant / Uncertain Mechanism: IgG (IAT) / IgM (IS) / Complement-activating / Mixed Dosage: Demonstrated / Not demonstrated Enzyme enhancement/destruction: Enhanced / Destroyed / Unaffected by enzyme Autoantibody component: Present / Absent / Suspected Hidden alloantibody exclusion: [list methods used — adsorption etc. and conclusion]

SECTION 7: CROSSMATCH RESULTS

Crossmatch Interpretation: Compatible / Incompatible Reason for incompatibility: [if applicable] Recommended action: [Issue / Do not issue / Repeat / Reference lab]

SECTION 8: INTEGRATED CLINICAL INTERPRETATION

Primary serological finding: [e.g., "Anti-E + Anti-c identified; IgG; AHG phase; dosage effect present"] Clinical significance: [Impact on transfusion, pregnancy, future testing] Patient phenotype concordance: [Patient confirmed E-negative, c-negative — consistent with antibody formation] Special situation assessment: [SCD / thalassaemia / obstetric / autoimmune]

SECTION 9: COMPONENT SELECTION RECOMMENDATION

Antigen-negative prevalence (to guide stock planning):

• E-negative: ~71% of donors
• c-negative: ~80% of donors
• E-negative AND c-negative: ~55% of donors
• (Adjust for local donor pool demographics)

SECTION 10: ACTION PLAN

IMMEDIATE:

• [Critical safety action — ABO check / do not issue / emergency notification]

SHORT-TERM (within 24–48h):

• [Confirm antibody with additional cells / enzyme panel / reference lab]
• [Extended phenotype patient's RBCs]
• [Notify patient's haematologist / obstetrician / primary team]

ONGOING MANAGEMENT:

• [Add permanent antibody alert to patient record — blood bank sticker / wristband / electronic flag]
• [Antibody card issued to patient]
• [Titration schedule if obstetric patient]
• [Molecular genotyping referral — if extended matching required]
• [Reference laboratory referral — if unresolved or high complexity]

CLINICIAN GUIDANCE:

• [Inform clinician of compatibility status]
• [Estimated time to find compatible blood]
• [Alternative strategies if compatible blood unavailable]

SECTION 11: BRIEF CLINICAL CONCLUSION

[3–5 sentence plain-language summary: what was found, its clinical significance, what blood to give, most important immediate action.]

PHASE 11 — IMAGE-SPECIFIC INTERPRETATION: UPLOADED PANELS

Analysis of Images 1, 2, 3, 4 (Patient Case Example)

Image 1 (Bio-Rad ID-DiaPanel — Panel A): Lot: 45161.25.x | Date: 2025.09.01 | Method: Gel CAT (IAT)

Panel Results:

Image 2 (Ortho Surgiscreen — 3-cell screen):

Image 3 (Bio-Rad ID-DiaPanel — Panel B, different lot): Lot: 45161.27.x | Date: 2025.09.29 | Autocontrol: 0

Image 4 (ID-DiaPanel-P — Empty template): Reference worksheet only (no patient results entered)

INTERPRETATION OF PATIENT CASE (Images 1–3):

Step 1 — Autocontrol: Image 3 shows A.C = 0 (negative). This is critical — confirms the antibody is most likely an ALLOANTIBODY, not an autoantibody. Proceed with alloantibody identification.

Step 2 — Surgiscreen (Image 2):

• Cell 1 (R₁ᵂR₁): +2 — This cell expresses D, C, Cw. Not e-negative; not c-negative.
• Cell 2 (R₂R₂): +2 — This cell expresses D, c, E. Notably c-positive and E-positive.
• Cell 3 (rr): 0 — Negative. This cell is D-negative, c-positive, e-positive, no C, no E.
• Pattern: Reacting with R₁R₁ (+2) AND R₂R₂ (+2), NOT with rr (0)
• Cells 1 and 2 share: D (in both). But also: Cell 1 has C/no E; Cell 2 has E/no C. Both have D.
• This is consistent with anti-D, or a combination. However, the rr cell is c-positive and negative — rules out anti-c. Need full panel to clarify.

Step 3 — Panel A (Image 1) Analysis:

Reactive cells: 1 (+1), 2 (+2), 3 (+3), 4 (+4), 6 (+2), 8 (+1), 9 (+2), 10 (+3) Non-reactive cells: 5 (0), 7 (0), 11 (0)

Looking for common antigen on cells 1,2,3,4,6,8,9,10 but NOT on 5,7,11:

• Cell 5 (ccddEe): has no D, has E, has c — negative
• Cell 7 (ccddee): no D, no E, has c — negative
• Cell 11 (ccddee): no D, no E, has c — negative

Looking at D: Cells 1,2,3,8 are D-positive (all reactive). Cell 4 is D-negative (r'r = Ccddee) but is +4 — most reactive cell. Cell 6 is rr (ccddee) D-negative but +2. Cells 9,10 are rr (ccddee) D-negative but +2,+3. So D cannot be the sole target — D-negative cells ARE reactive.

Looking at C: Cell 1 (CCC*D.ee) has C — reactive. Cell 4 (Ccddee) has C — very reactive (+4). Cell 8 (ccD.ee) has NO C — reactive (+1). So C cannot be sole target.

Reconsidering: What's common to all REACTIVE cells (1,2,3,4,6,8,9,10) and ABSENT from all NEGATIVE cells (5,7,11)?

Cell 4 = Ccddee = has C, c, d (no D), no E — reaction +4 Cell 5 = ccddEe = has c, E, no C, no D — NEGATIVE Cell 6 = ccddee = has c, no E, no C, no D — +2 Cell 7 = ccddee = rr — NEGATIVE Cell 11 = ccddee = rr — NEGATIVE

Cells 6,7,11 are all ccddee (rr) — same phenotype! Yet 6 = +2, 7 = 0, 11 = 0. This suggests a SECOND ANTIBODY or additional antigen involved, OR HLA antibody (Cell 9 flagged HLA+).

Checking Cell 9 (rr with HLA+): +2. Cell 6 (rr): +2. Cell 7 (rr): 0. Cell 11 (rr): 0.

The additional differentiation between rr cells must be in non-Rh antigens. Looking at MNS, Duffy, Kidd columns across rr cells (6,7,9,10,11):

Cell 6: ccddee, rr — has specific Kell, MNS, Duffy, Kidd antigens (from panel design). Reactive. Cell 7: ccddee, rr — different antigen combination. Non-reactive. Cell 9: ccddee, rr — HLA+ flag; different non-Rh antigens. Reactive. Cell 10: ccddee, rr — reactive +3. Cell 11: ccddee, rr — non-reactive.

This pattern among the rr cells is crucial. The overall picture most likely represents:

Panel A Preliminary Conclusion: MULTIPLE ANTIBODIES — likely anti-C + another antibody

Anti-C evidence:

• Cell 4 (Ccddee, r'r) = +4 strongest reaction — homozygous for C (double dose C)
• Cell 1 (CCC*D.ee) = +1 — C-positive
• Cell 2 (CCD.ee) = +2 — C-positive
• Cell 3 (ccD.EE) = +3 — *** c-positive, no C — this contradicts anti-C alone ***

So anti-C cannot be sole antibody either, as Cell 3 (ccD.EE — C-NEGATIVE) is reactive +3.

Revised analysis — antibody directed at antigen(s) present on:

• Cell 3 (ccD.EE) +3: has D, E, c
• Cell 4 (Ccddee r'r) +4: has C, c (no D, no E) — most reactive

What is shared between Cell 3 and Cell 4 that is absent from Cell 5 (ccddEe, negative) and Cell 11 (ccddee, negative)?

Cell 3 has: D, c, E (no C) Cell 4 has: C, c (no D, no E) Cell 5 has: c, E (no D, no C) — NEGATIVE Cell 11 has: c (no D, no C, no E) — NEGATIVE

Shared between 3 and 4 but NOT 5: D (present in 3, absent in both 4 and 5 — no), C (in 4, not in 3)...

Actually the strongest clue: Cell 4 is maximally reactive (+4) and is Ccddee. Among reactive cells, the variation in strength (1,2,3,4,2,1,2,3) correlates with antigen expression. Most reactive = Cell 4 (Ccddee = homozygous C, homozygous c). This is the c homozygous double-dose expression (cc).

Panel B (Image 3) — key verification: Cell 4 (Ccddee, r'r) = +2 only on Panel B Cells 1,2,3 (D-positive) = ALL ZERO on Panel B Cells 5–11 (except 4 and 11) = all ZERO

Panel B Cell 4 = +2 (C+, c+, no D, no E) Panel B Cell 11 = +2 (rr, ccddee)

Between the two panels: Panel A shows broad reactivity; Panel B shows only Cells 4 and 11 reactive.

The reconciliation: Panel A was likely tested with a DIFFERENT serum (possibly before treatment or at a higher titre), OR Panel A shows multiple specificities and Panel B performed at a different time shows only residual weaker antibody.

Most probable final interpretation:

Given:

• Negative autocontrol on Panel B
• Surgiscreen: R₁R₁ +2, R₂R₂ +2, rr 0
• Panel A broad reactivity across D-positive AND some D-negative cells with C
• Panel B: only Cell 4 (r'r = Ccddee) and Cell 11 (rr) reactive

The most consistent identification is:

Anti-C — explains Cell 4 reactivity (C-homozygous = strongest reaction), Cell 1 (C+), Cell 2 (C+) on Panel A, and positive Surgiscreen cells 1 and 2 (both C+)

PLUS an additional antibody to explain Cell 3 (ccD.EE, C-negative) being +3 and rr cell reactivity — most likely anti-E (Cell 3 is EE homozygous, would give strong reaction) or anti-Rh antigen.

Panel B supports: Panel B Cell 4 (Cc) = +2, Cell 11 (rr ccddee — need antigen table) = +2. If Cell 11 has E+ antigen (from panel design) = anti-E may persist at lower titre.

Working antibody identification: Anti-C + Anti-E (most probable)

• Both are clinically significant IgG Rh alloantibodies
• Consistent with previous Rh sensitisation (transfusion or pregnancy)
• Patient is likely phenotype: D+/C-/E-/c+/e+ or variant

Blood requirements:

• C-negative AND E-negative
• ABO and Rh(D) compatible
• Leucodepleted
• Crossmatch compatible at AHG phase
• C-negative E-negative blood available in ~55% of donors

Clinical urgency: Proceed with reference laboratory confirmation. Provide patient with antibody alert card. All future transfusions must be C-negative and E-negative.

HLA antibody note (Cells 5, 9 flagged): These are informational flags indicating donor cells with known HLA antigens that may cause false reactions in patients with HLA antibodies. Do not interpret HLA flags as alloantibody confirmation. However, consider requesting leucodepleted blood to reduce HLA alloimmunisation risk going forward.

SKILL USAGE NOTES

Trigger phrases:

"Interpret this antibody identification panel", "What antibody does this panel show?", "Interpret my crossmatch result", "Is this DAT positive significant?", "What blood can I give this patient?", "Interpret my ID-DiaPanel results", "What does this Surgiscreen show?", "Interpret antibody titration", "HDFN monitoring", "Sickle cell transfusion advice", "Patient has warm autoantibody — what blood?", "Antenatal antibody found", "How do I manage this complex antibody case?", "Crossmatch incompatible — what now?"

Mandatory inputs:

1. Panel image(s) or typed results
2. Patient ABO/Rh type
3. Patient age and sex
4. Clinical context
5. Autocontrol result (CRITICAL)

Always ask if not provided:

• Transfusion history (within last 3 months)
• Obstetric history
• Medications (especially daratumumab)
• Phase of testing performed
• Patient's known phenotype/genotype

Output modes:

EEHLSS / MedLabAI-LIS | Maintained by Echukwuka | Version 1.0 — April 2026 Aligned to: ISBT · AABB Technical Manual 20th Ed · BCSH/BSH Transfusion Guidelines · RCPath · ISO 15189:2022 · CBAHI · CAP Transfusion Medicine Checklist All interpretations require validation by a qualified Biomedical Scientist, Medical Laboratory Scientist, or Transfusion Medicine Physician. This skill provides expert decision support only — complex cases must be referred to a Transfusion Medicine specialist or Reference Laboratory.