HIS07 Classification And Laboratory Diagnosis Of Anaemia II Flashcards
Approach to anaemia
Always correlate Lab result with Clinical context
1. MCV
2. Other RBC indices
3. Reticulocyte count
4. Other cell lines, lineages affected
5. Blood film examination
—> Correlate with clinical context —> Other appropriate investigations for Definitive Diagnosis
Case 1:
- 68 years old well built man c/o constipation
- P/E: Pallor only
- Blood biochemistry: Normal liver, renal function tests
- ↓↓ Hb, RBC count
- ↓ MCV, MCH, MCHC
- ↑ RDW, PLT
- Reticulocyte not raised
- Hypochromic Microcytic, Central pallor
- Size and shape variation
- Pencil cells, Target
- No Polychromasia (i.e. No Reticulocytosis)
- Reactive thrombocytosis
- ↓ MCV
—> Microcytic anaemia
—> Thalassaemia / Fe deficiency - Pencil cells, Reactive thromobcytosis —> Fe deficiency
- ↑ RDW, ↓↓ RBC (not enough Fe to make RBC) —> Fe deficiency
(Thalassaemia: normal RDW, usually normal RBC count, just abnormal Hb)
- Biochemical findings:
- Low serum Fe (usable Fe)
- Low serum Ferritin (storage Fe)
- High serum Transferrin (compensatory response to ↑ transport of Fe) —> ↑TIBC
- Low Transferrin saturation
—> Confirm Fe deficiency
Treatment: Oral iron replacement
However, Iron deficiency anaemia is NOT a disease —> must find CAUSE
—> Patient c/o constipation (lower GI tract)
—> Stool for occult blood +ve (GIT blood loss)
—> Colonoscopy with biopsy
—> Adenocarcinoma (Fe deficiency anaemia very common in colorectal cancer)
Reason for not raised Reticulocyte despite bleeding (vs reticulocytosis in acute bleeding):
- NOT enough raw materials (Fe) to make Reticulocyte
- 記住!!! Reticulocytosis ***前提: Kidney normal, BM function normal, Adequate raw material!!!
***Interpretation of Iron profile
- Fe deficiency
MCV/MCH: ↓, proportional to severity of anaemia
Serum Fe: ↓
TIBC: ↑ (High Transferrin —> compensatory response to ↑ transport of Fe)
Serum Ferritin: ***↓
BM Iron store: -ve
Erythroid Iron: -ve - Anaemia of chronic illness
Inflammation —> Cytokines (IL-6) —> ↑ Hepcidin production —> ↓ Fe release in macrophage, ↓ absorption of Fe in GI tract —> Fe block (block absorption of Fe by erythroblasts in BM)
MCV/MCH: Normal / slightly ↓
Serum Fe: ↓
TIBC: ↓ (↓ Transferrin —> stop absorbing Fe + stop binding Fe from macrophage)
Serum Ferritin: ***↑ (↓ Fe release in macrophage + Acute phase reactant: ↑ in inflammation —> keep Fe away from pathogens)
BM Iron store: +ve
Erythroid Iron: -ve
- Thalassaemia trait
MCV/MCH: ***↓, disproportional to severity of anaemia
Serum Fe: Normal
TIBC: Normal
Serum Ferritin: Normal / ↑
BM Iron store: +ve
Erythroid Iron: +ve
Common causes of Fe deficiency
- Blood loss!!!!!!!!
- Increased demand (pregnancy, puberty)
- Poor intake / Malabsorption (low daily requirement) (GI tract problem)
Common sites of blood loss
- GI tract (GI bleeding)
—> ***Stool for occult blood - Genital tract (menorrhagia)
- Urinary tract (haematuria)
Case 2:
- 70-year old man
- required regular transfusion for chronic anaemia due to chronic renal failure
- one day he was scheduled to have blood transfusion in day ward
CBP result (pre-transfusion):
- Hb 5.0 (very anaemic)
- WBC within normal range
- PLT borderline
- MCV 82 (normocytic)
Chronic anaemia due to Chronic renal failure —> Normocytic
BUT
- Baseline Hb 7-8 g/dL
- NO pallor
- Repeated Hb —> 10 g/dL
Causes:
- mix-up blood sample with other patients
—> Patient identification MOST important
—> always correlate blood result with clinical context, don’t just treat the number
Treatment:
- No need blood transfusion
Case 3:
- female 72 year old
- DM, HT
- admitted for symptomatic anaemia
CBC:
- ↓↓ Hb, RBC
- ↓ WBC, PLT
- ↑ MCV, RDW
- Reticulocyte not raised
Biochemistry:
- Bilirubin slightly ↑
- LDH markedly ↑
Blood smear:
- large oval RBC (Ovalmacrocyte)
- Hypersegmented neutrophil (>= 6 lobes / >3% of >=5 lobes neutrophil)
- ↑ MCV
—> Macrocytic
—> Megaloblastic anaemia / Severe haemolysis (∵ marked reticulocytosis) / Aplastic anaemia / Myelodysplasia - Reticulocyte not raised —> NOT haemolysis
- ↓ RBC, WBC, PLT
—> ***Pancytopenia
—> Megaloblastic anaemia / Aplastic anaemia / Myelodysplasia - Order peripheral blood smear first (Definitely needed for investigation of anaemia) before BM examination!!!
- look for pathological features
—> can be diagnostic / rule out other DDx without BM examination
- blood film can confirm degree of reticulocytosis + pathological features of haemolytic anaemia
- blood film show dysplastic features (Myelodysplasia) —> BM exam
- if no clue from blood film —> BM exam
This case:
- **Oval macrocyte
—> characteristic of Megaloblastic anaemia
- **Hypersegmented neutrophil
Confirmation:
- ***Active B12 ↓↓
- Serum folate normal
—> Megaloblastic anaemia
**Elevated LDH, **Jaundice:
B12 deficiency
—> Nucleotide synthesis impaired
—> Maturation of RBC impaired
—> Ineffective haemopoiesis (due to B12 deficiency)
—> Erythroid precursors (Hypercellular in BM) prematurely broken down in marrow
—> Elevated LDH (intracellular enzyme)
***Pancytopenia:
B12 deficiency
—> Nucleotide synthesis impaired
—> Maturation of ALL cell lineages impaired
Case 4:
- 47yo female
- good past health
- present with SOB on exertion
- tiredness
Physical examination:
- Pallor
- Jaundice
- No LN
- No hepatosplenomegaly
- Vitals stable
CBC:
- ↓↓ Hb
- ↓ RBC
- ↑ MCV, MCHC, RDW, WBC (slight)
Other blood result:
- Renal function normal
- Liver function:
—> Bilirubin ↑ (predominantly indirect / unconjugated bilirubin) —> Jaundice
—> ALP 54 (biliary ductal enzyme) (normal)
—> ALT 7 (parenchymal enzyme) (normal)
Further blood test:
- LDH ↑↑
- Reticulocyte ↑↑
- ↑ MCV
—> Macrocytic
—> Megaloblastic anaemia / Severe haemolysis / Aplastic anaemia / Myelodysplasia - Reticulocyte ↑
—> NOT BM production failure - No Splenomegaly
—> NOT sequestration - No context of dilution
- Unconjugated Bilirubin + LDH ↑
—> Excessive RBC destruction - High Reticulocytosis
—> NOT Megaloblastic anaemia (∵ B12, folate should be low in Megaloblastic anaemia —> no raw materials for Reticulocytosis)
—> NOT Aplastic anaemia (∵ failed BM in Aplastic anaemia —> cannot produce Reticulocytes)
—> NOT Myelodysplasia (∵ mature cells will die excessively in circulation due to mutation —> no Reticulocytosis)
Conclusion: Haemolytic anaemia
Find out cause of Haemolytic anaemia
7. Peripheral blood smear
- Spherocyte (no central pallor, smaller, denser)
(due to damaged RBC membrane
—> loss of SA / volume ratio
—> fold into sphere)
- Reticulocytosis + Spherocytosis
—> Warm AIHA (autoimmune haemolytic anaemia) OR Hereditary spherocytosis - Distinguish between warm AIHA / Hereditary spherocytosis
—> DAT (direct anti-globulin test) strongly +ve
—> IgG +ve (warm AutoAb)
—> C3d -ve (see whether cold AIHA)
—> Warm AIHA
Final Dx: Warm AIHA
***Haemolytic anaemia
To make Diagnosis:
1. Evidence of RBC **destruction
- ↑ Indirect Bilirubin
- ↑ LDH +/- Markers of intravascular haemolysis (extravascular: Reticuloendothelial system)
AND
2. Evidence of ↑ RBC **production
- Reticulocytosis
To find out Cause:
Peripheral blood smear
Causes:
Intrinsic (within RBC)
1. **Membrane defect
2. **Enzyme defect (e.g. G6PDD) (Red cell enzymopathy)
3. ***Hb defect (Haemoglobinopathy)
Extrinsic (outside RBC)
1. Ab-mediated (Alloimmune, Autoimmune, Drug-induced)
2. **Mechanical damage (*Microangiopathic haemolytic anaemia, mechanical heart valves)
3. Burn
4. Toxin
5. Infection
***AIHA (autoimmune haemolytic anaemia)
Haemolytic anaemia
+
Presence of ***Auto-Ab on own RBC
Warm AIHA:
- AutoAb: **IgG on RBC membrane
- Reaction of IgG coating on RBC occurs at **37oC
- **Extravascular haemolysis (∵ RBC membrane damaged by **reticuloendothelial system —> Spherocytes)
- **Spherocytosis
- **Causes: Idiopathic, **Drugs (Methyldopa, Rifampicin), **Autoimmune disease, CLPD etc.
Cold AIHA:
- AutoAb: **IgM on RBC membrane
- Reaction of IgM coating on RBC occurs at **30-32oC (usually happen in periphery body)
- **Intravascular Haemolysis (∵ IgM fix complement —> RBC lysis by **C5-9 MAC)
- **RBC agglutination (at cold temperature)
- **Causes: Infection (e.g. Mycoplasma), CLPD
***Always need to find out secondary causes for AIHA, esp. CLPD (Chronic Lymphoproliferative Disorders)
***Intravascular haemolysis
RBC damaged in circulation
—> release free Hb (↑ plasma Hb)
—> Free Hb bind to Haptoglobin first (↓ Haptoglobin)
—> Haptoglobin used up
—> Hb bind to Albumin (↑ Methaemalbumin, +ve Schumm’s test)
—> Excess Hb:
1. Haemoglobinaemia
2. Filter in glomerulus (Haemoglobinuria —> Dark urine)
3. Iron deposition in renal tubules (Haemosiderin) —> re-excreted in urine inside dislodged cells (***Haemosiderinuria: Sign of chronic intravascular haemolysis)
***Diagnosis of AIHA
- Haemolytic anaemia
- Peripheral Blood Smear
- **Spherocytes —> Warm AIHA
- **RBC agglutination (at cold temperature) —> Cold AIHA - DAT +ve
- RBC coated with **IgG —> Warm AIHA
- RBC coated with **C3d (usually IgM cannot be detected) —> check cold agglutinin titre —> if high —> Cold AIHA
***Direct antiglobulin test (DAT)
DAT / Coombs’ test
- Confirm presence of Ig / Complement on RBC
- Find out what type of Ig / Complement coated
Patient’s isolated + washed RBC are incubated with Antihuman Ab (Coombs reagent)
—> ***RBC agglutinate
—> Antihuman Ab form links between RBC by binding to human Ab on RBC
**Anti-IgG —> cause RBC in Warm AIHA to clump together
**Anti-C3d —> cause RBC in Cold AIHA to clump together
However:
DAT +ve —> Not necessarily AIHA
- only showed Ab/complement coated on RBC
- occur in healthy individual (can be non-haemolysis related)
- rate even higher in hospitalised patients
Therefore:
- DAT +ve only prove whether haemolysis is immune-mediated
3 types:
1. Autoimmune (AIHA)
2. Alloimmune (Ab from someone else)
3. Drug-mediated (Drug trigger Ab reaction)
—> DAT does NOT distinguish between these 3 types!!!
DON’T mix up with Indirect antiglobulin test (IAT)!!!
—> Test ***free Ab in patient’s serum (NOT RBC!!!)
Case 5:
- 30 yo female
- previously healthy
- fever
- clouded consciousness
Physical examination:
- Fever
- Jaundice
- Pallor
- Mentally slow
CNS:
CT brain normal
CSF examination normal
Blood biochemistry:
- High creatinine
- normal Na/K
- normal glucose
- normal liver enzymes
- ↑ Bilirubin level
- ↑ LDH
CBC:
- ↓↓ Hb, RBC, PLT
- ↑↑ RDW
- ↑ Reticulocyte
- MCV normal
- Clouded consciousness
—> Involve CNS / Electrolyte imbalance (Ca/Na/K) / Glucose level (rule out hypoglycaemia)
—> CNS infection also a DDx
—> CT brain + CSF examination - MCV normal
—> Normocytic anaemia (Anaemia of chronic disease / Chronic renal failure) - Previously healthy
—> NOT anaemia of chronic disease - High creatinine
—> Acute renal failure (BUT NOT chronic ∵ Reticulocytosis) - BM failure, RBC Destruction, Sequestration, Dilution
—> NO BM failure (∵ Reticulocytosis)
—> NO Sequestration (∵ NO Splenomegaly)
—> NO Dilution (∵ NO context)
—> conclusion: RBC Destruction - Reticulocytosis (“normal” Kidney, normal BM, enough raw material (no folate / B12 deficiency))
—> NOT Megaloblastic anaemia
—> NOT Aplastic anaemia
—> NOT Myelodysplasia - ↑ Bilirubin level,↑ LDH + Reticulocytosis
—> Haemolytic anaemia
Find out cause of Haemolytic anaemia
- Peripheral blood smear
- Polychromasia (Reticulocytosis)
- Nucleated RBC (Bone marrow trying hard to compensate, rate of production fast, spleen have no time to remove nucleus)
- **Red cell fragment
- **Thrombocytopenia
Conclusion: Microangiopathic (Severe) haemolytic anaemia
Final Dx: Thrombotic thrombocytopenic purpura (TTP) (one of disease category in Microangiopathic haemolytic anaemia)
Why is MCV normal despite severe haemolytic anaemia?
—> Due to presence of Red cell fragments
***Microangiopathic haemolytic anaemia
Some disease processes activate platelets
—> Platelets aggregate
—> Platelet plugging (clot) in microcirculation
—> RBC pass through clot
—> RBC damaged by clot
—> Lysed in circulation
Thrombotic thrombocytopenic purpura (TTP):
Classical Pentad:
1. Fever
2. **Fluctuating neurological signs
3. **Impaired renal function
4. **Red cell fragmentation
5. **Thrombocytopenia
