Haemolytic Anaemia — When the Body Destroys Its Own Red Blood Cells

When Red Cells Die Too Soon: The Laboratory Diagnosis of Haemolytic Anaemia

Red blood cells are extraordinary structures. Stripped of their nuclei and organelles, they pack their cytoplasm with approximately 270 million haemoglobin molecules each, designed for a single purpose: transporting oxygen from the lungs to every tissue in the body. They are flexible enough to squeeze through capillaries narrower than their own diameter, resilient enough to withstand the turbulent flow of the bloodstream, and durable enough to survive for approximately 120 days before being quietly retired by the spleen.

But in haemolytic anaemia, red cells are destroyed prematurely — days, weeks, or months before their time — overwhelming the bone marrow's ability to compensate. The bone marrow can increase red cell production up to six- to eightfold in response to haemolysis, but even this remarkable capacity has its limits. When destruction outpaces production, anaemia develops, with a unique biochemical fingerprint that the laboratory can detect and interpret.

Haemolytic anaemia is not a single disease but a broad category of conditions with many causes — some inherited (passed through generations), some acquired (triggered by infection, drugs, autoimmunity). Understanding these conditions, their mechanisms, and the tests used to investigate them is a core competency for any medical laboratory scientist. In Ghana and West Africa, where sickle cell disease, G6PD deficiency, and malaria are prevalent, this knowledge is not academic — it is essential to patient care.

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1. What Happens When Red Cells Are Destroyed?

When red cells lyse (break down), their contents — primarily haemoglobin — are released into the body. The body handles this through two main pathways, and distinguishing between them is the first step in the diagnostic approach.

1.1 Intravascular Haemolysis: Destruction in the Circulation

Red cells lyse directly within blood vessels. Free haemoglobin is released into plasma, where it binds to haptoglobin — a scavenger protein that clears haemoglobin and prevents it from damaging the kidneys. The haptoglobin-haemoglobin complex is rapidly cleared by the liver.

When haemolysis is brisk:

• Haptoglobin becomes depleted (low or undetectable)

• Free haemoglobin appears in plasma — haemoglobinaemia

• When plasma haptoglobin is exhausted and the renal threshold is exceeded, free haemoglobin spills into the urine — haemoglobinuria

Haemoglobinuria is a hallmark of intravascular haemolysis. The urine appears red-brown (like cola or strong tea). A positive dipstick for blood with no red cells on microscopy confirms haemoglobinuria.

Chronic intravascular haemolysis leads to haemosiderinuria — haemosiderin (iron storage complexes) deposits in renal tubular cells and is shed in the urine. Detected by Prussian blue staining of urine sediment, haemosiderinuria is a sensitive indicator of ongoing intravascular haemolysis.

1.2 Extravascular Haemolysis: Destruction in the Spleen and Liver

Most haemolysis is extravascular. Red cells are engulfed by macrophages in the spleen, liver, and bone marrow (the reticuloendothelial system) — not because they burst, but because they are recognised as abnormal or aged.

Inside the macrophage:

• Haemoglobin is broken down into globin (recycled) and haem

• Haem is converted to biliverdin, then to unconjugated (indirect) bilirubin

• Bilirubin is released into plasma, transported to the liver, conjugated with glucuronic acid, and excreted in bile

Consequences:

• Elevated unconjugated bilirubin causes jaundice (yellowing of skin and eyes)

• Increased bilirubin in bile leads to the formation of bilirubin gallstones (cholelithiasis) in chronic haemolysis — a common complication in sickle cell disease and hereditary spherocytosis

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2. General Laboratory Markers of Haemolysis: The Signature of Destruction

Regardless of the underlying cause, active haemolysis leaves a characteristic laboratory signature. Finding these markers together points to haemolysis as the cause of anaemia.

Marker	Finding in Haemolysis	Mechanism
Haemoglobin	Low	Red cell destruction exceeds production
Reticulocyte count / Reticulocyte production index	Elevated	Bone marrow compensates by releasing immature red cells earlier. Reticulocytosis is a hallmark of haemolytic anaemia.
LDH (lactate dehydrogenase)	Markedly elevated	Released from the cytoplasm of lysed red cells. LDH is often strikingly high in intravascular haemolysis.
Haptoglobin	Low or absent	Consumed as it binds free haemoglobin. Low haptoglobin is one of the most sensitive markers of haemolysis.
Unconjugated (indirect) bilirubin	Elevated	From haem breakdown in macrophages. Unconjugated bilirubin is not water-soluble; it does not appear in urine.
Haemoglobinaemia / haemoglobinuria	Present	In intravascular haemolysis
Haemosiderinuria	Present	In chronic intravascular haemolysis (detected by Prussian blue stain)

On the blood film:

• Polychromasia — blue-tinged red cells that are larger than normal. These are reticulocytes (immature red cells released early from the marrow). Their presence confirms bone marrow compensation.

• Specific morphological abnormalities — depending on the cause (sickle cells, spherocytes, schistocytes, bite cells)

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3. Inherited Haemolytic Anaemias: Genetic Defects

3.1 Sickle Cell Disease (SCD): The West African Burden

Sickle cell disease is caused by a point mutation in the beta-globin gene — adenine replaced by thymine at codon 6, changing the amino acid from glutamic acid to valine. This produces Haemoglobin S (HbS) .

When HbS is deoxygenated, it polymerises into long chains that distort the red cell into a rigid, crescent-shaped sickle cell. Sickled cells are:

• Fragile — they haemolyse easily (haemolytic anaemia)

• Sticky — they adhere to endothelium and to each other, causing vascular occlusion (painful vaso-occlusive crises, acute chest syndrome, stroke, and chronic organ damage)

SCD in West Africa:

Sub-Saharan Africa bears the highest burden of sickle cell disease in the world. In Ghana, the HbS allele frequency is among the highest globally — approximately 1–2% of children are born with HbSS (sickle cell anaemia) , and 20–30% carry the sickle cell trait (HbAS) . This high prevalence is a legacy of balanced polymorphism — the HbAS heterozygous state provides partial protection against Plasmodium falciparum malaria, a selective advantage that maintained the HbS allele in malaria-endemic regions.

Laboratory Features of Sickle Cell Disease:

Test	Finding
Haemoglobin	6–10 g/dL (chronic anaemia; baseline varies)
Blood film	Sickle cells (crescent-shaped), target cells, polychromasia (reticulocytes), Howell-Jolly bodies (due to functional hyposplenism from repeated infarction), boat-shaped cells
Haemoglobin electrophoresis / HPLC	Confirms HbSS (HbS ~80–95%, HbF elevated, HbA2 normal or slightly elevated). Distinguishes from HbSC (HbS + HbC), HbS-beta thalassaemia, and sickle cell trait (HbAS)
Reticulocyte count	Elevated (typically 5–15%)
LDH, bilirubin, haptoglobin	Elevated LDH, elevated unconjugated bilirubin, low haptoglobin — consistent with ongoing haemolysis
Sickle solubility test (Sicklequick)	Useful screening test; detects presence of HbS but does not distinguish HbSS from HbAS or HbSC. Positive in both sickle cell disease and sickle cell trait

Screening and Diagnosis:

• Newborn screening is essential for early diagnosis and initiation of preventive care (penicillin prophylaxis, vaccination, education)

• HPLC (high-performance liquid chromatography) is the preferred method for diagnosis and quantification of haemoglobin fractions

3.2 Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency: The Oxidative Stress Vulnerability

G6PD is an enzyme critical to the hexose monophosphate shunt — the pathway that generates NADPH, which protects red cells from oxidative damage. Red cells lack mitochondria and rely entirely on this pathway to neutralise reactive oxygen species.

G6PD deficiency is:

• X-linked — males are hemizygous (one affected X chromosome) and express the deficiency; females can be heterozygous carriers (variable expression due to X-inactivation)

• The most common enzyme deficiency worldwide — affecting over 400 million people

• Particularly prevalent in malaria-endemic regions like West Africa, where the deficiency may confer some protection against P. falciparum malaria

Clinical Presentation:

Most individuals with G6PD deficiency are asymptomatic at baseline. They develop acute haemolytic anaemia when exposed to oxidative stressors:

Category	Triggers
Drugs	Primaquine, dapsone, sulfonamides, nitrofurantoin, rasburicase
Food	Fava beans (favism) — more common in Mediterranean variants
Infection	Bacterial or viral infections (especially typhoid fever, pneumonia, hepatitis)
Other	Diabetic ketoacidosis, severe metabolic stress

Laboratory Findings During a Haemolytic Episode:

• Falling haemoglobin — often dramatic (2–4 g/dL drop over 24–48 hours)

• Elevated LDH, low haptoglobin

• Blood film: Bite cells (degmacytes) — red cells with a "bite" taken out where the spleen has removed oxidised haemoglobin; blister cells; Heinz bodies (on supravital staining with crystal violet) — aggregates of denatured haemoglobin attached to the red cell membrane

• G6PD enzyme assay: Low or absent activity

Critical Note: G6PD enzyme assay can be falsely normal during acute haemolysis because the oldest, most deficient cells have already lysed. The surviving cells are younger and have near-normal enzyme activity. Test after recovery (2–3 months) for accurate diagnosis.

3.3 Hereditary Spherocytosis (HS): The Membrane Defect

Hereditary spherocytosis is caused by defects in red cell membrane proteins — most commonly spectrin, ankyrin, band 3, or protein 4.2. These defects lead to loss of membrane surface area — the red cell loses its biconcave disc shape and becomes a sphere (spherocyte).

Why Spherocytes Haemolyse:

Spherocytes have reduced deformability. They cannot squeeze through the splenic sinusoids and are trapped in the spleen, where they are destroyed by macrophages. Splenectomy dramatically improves haemolysis in HS.

Laboratory Features:

Test	Finding
Blood film	Spherocytes — round cells with no central pallor (normal red cells have central pallor ~1/3 of diameter)
MCHC (mean corpuscular haemoglobin concentration)	Elevated (>360 g/L) — a unique feature of HS. Spherocytes have lost membrane but retained haemoglobin, so haemoglobin is more concentrated.
Osmotic fragility	Increased — spherocytes lyse at higher NaCl concentrations than normal red cells (classic test, less used now)
EMA binding test (eosin-5-maleimide)	Reduced — EMA binds to band 3 protein; reduced binding is the modern gold standard for HS diagnosis (sensitivity >90%)

3.4 Thalassaemia: The Globin Chain Imbalance

Thalassaemias are caused by mutations in the alpha- or beta-globin genes, leading to imbalanced globin chain production. Excess globin chains precipitate inside red cells, causing intramedullary destruction (ineffective erythropoiesis) and peripheral haemolysis.

Type	Mechanism	Laboratory Features
Beta-thalassaemia major	Homozygous or compound heterozygous beta-globin mutations → severe reduction or absence of beta chains	Severe transfusion-dependent haemolytic anaemia. HbF markedly elevated, HbA2 elevated (on HPLC). Blood film: microcytic hypochromic red cells, target cells, nucleated red cells, basophilic stippling.
Alpha-thalassaemia	Deletion or inactivation of alpha-globin genes	Common in West Africa. HbH disease (3 gene deletions) — moderate haemolytic anaemia. HbH (4 beta chains) detected on HPLC. Silent carrier and trait states are asymptomatic.

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4. Acquired Haemolytic Anaemias: Immune and Mechanical Destruction

4.1 Autoimmune Haemolytic Anaemia (AIHA): The Body Against Itself

In AIHA, the immune system produces antibodies against the patient's own red cell antigens. There are two major types, distinguished by the temperature at which the antibodies react:

Type	Antibody	Temperature	Features	DAT (Coombs)
Warm AIHA	IgG	37°C	Most common type. Spherocytes on blood film. Associated with autoimmune diseases (SLE), lymphoproliferative disorders, or idiopathic.	IgG positive (often + C3d)
Cold AIHA	IgM (cold agglutinin)	Low temperatures (<30°C)	Agglutination of red cells in peripheral blood (visible on film). Acrocyanosis (blue discoloration of fingers/toes in cold). Often post-infectious (Mycoplasma, EBV) or associated with lymphoproliferative disorders.	C3d positive (IgG negative)

The Direct Antiglobulin Test (DAT, Coombs Test):

The DAT is the key investigation for AIHA. It detects antibodies or complement proteins coated on the red cell surface.

• Procedure: Patient's red cells are washed and mixed with anti-IgG and anti-C3d reagents. Agglutination indicates a positive result.

• Interpretation: Positive DAT confirms immune-mediated red cell coating. The pattern (IgG alone, C3d alone, or both) suggests the mechanism.

Note: A negative DAT does not completely exclude AIHA (low-affinity antibodies may be missed), but positive DAT in a patient with haemolytic anaemia is diagnostic.

4.2 Microangiopathic Haemolytic Anaemia (MAHA): Physical Destruction

MAHA occurs when red cells are physically shredded by:

• Fibrin strands deposited in small vessels (in DIC, TTP, HUS)

• Abnormal microvasculature (malignant hypertension, HELLP syndrome in pregnancy)

• Mechanical heart valves

Causes of MAHA:

• TTP (thrombotic thrombocytopenic purpura) — ADAMTS13 deficiency → unchecked ultra-large vWF multimers → platelet thrombi → schistocytes, severe thrombocytopenia

• HUS (haemolytic uraemic syndrome) — often Shiga toxin-producing E. coli (STEC-HUS) or complement-mediated (atypical HUS)

• DIC (disseminated intravascular coagulation) — consumptive coagulopathy

• Malignant hypertension

• HELLP syndrome (Haemolysis, Elevated Liver enzymes, Low Platelets) in pregnancy

• Prosthetic heart valves

The Blood Film in MAHA:

Schistocytes — fragmented red cells — are the hallmark. Look for:

• Helmet cells (fragments with pointed ends)

• Triangle cells

• Keratocytes (horn-shaped fragments)

Critical Reporting: The presence of schistocytes in a patient with anaemia, thrombocytopenia, and renal impairment or neurological symptoms suggests TTP or HUS — a medical emergency. This finding must be reported urgently.

4.3 Malaria-Associated Haemolysis: The Regional Burden

Plasmodium falciparum, the predominant species in West Africa, causes haemolytic anaemia through multiple mechanisms:

• Direct haemolysis: Rupture of infected red cells at schizogony (release of merozoites)

• Bystander haemolysis: Complement-mediated destruction of uninfected red cells

• Dyserythropoiesis: Impaired red cell production during acute infection

Severe malaria with high parasitaemia can cause profound haemolytic anaemia requiring urgent transfusion. In young children and pregnant women, anaemia is a major contributor to malaria mortality.

Blackwater Fever:

A severe complication of malaria (historically associated with quinine use) characterised by:

• Massive intravascular haemolysis

• Haemoglobinuria — urine turns black (hence the name)

• Acute kidney injury

Blackwater fever occurs most frequently in patients with G6PD deficiency who are treated with oxidant antimalarials (primaquine) or quinine. It remains a clinical challenge in malaria-endemic regions.

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5. Approach to Laboratory Investigation of Haemolytic Anaemia

A structured approach ensures the correct diagnosis and avoids unnecessary testing.

Step	Investigation	Purpose
Step 1: Confirm haemolysis	Reticulocyte count, LDH, unconjugated bilirubin, haptoglobin	Establishes that haemolysis is present
Step 2: Determine intravascular vs extravascular	Haemoglobinuria, haemoglobinaemia, haemosiderinuria	Localises the site of destruction
Step 3: Examine the blood film	Morphology: sickle cells, spherocytes, schistocytes, bite cells, Heinz bodies	Identifies specific causes
Step 4: Targeted investigations	DAT (AIHA), G6PD assay, HPLC (haemoglobinopathies), osmotic fragility/EMA binding (HS)	Confirms specific diagnosis
Step 5: Correlate with clinical history	Ethnicity, family history, drug history, travel history, infection history	Contextualises findings

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Conclusion: A Diagnostic Journey

Haemolytic anaemia is a diagnostic journey — from the clinical picture, through the CBC and blood film, to targeted specialist tests. For the medical laboratory scientist, recognising the hallmarks of haemolysis and correctly classifying the morphological abnormalities on the blood film are critical skills.

In Ghana and West Africa, the high prevalence of sickle cell disease, G6PD deficiency, and malaria makes haemolytic anaemia an everyday clinical challenge. The blood film that shows sickle cells in a child with fever and bone pain. The G6PD assay that explains why a patient haemolysed after primaquine. The schistocytes that signal TTP and prompt plasma exchange. The spherocytes that reveal hereditary spherocytosis and explain lifelong anaemia.

Master these concepts, and you will be an indispensable member of the diagnostic team.

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Your Results. Your Understanding. Your Health.

Whether you're a patient navigating a haemolytic anaemia diagnosis, a healthcare professional interpreting complex haematological results, or someone seeking to understand these conditions, knowledge is essential.

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