Haemolytic Anaemia Workup
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Direct answer
Haemolysis is proved by a triad that costs almost nothing — reticulocytosis, raised LDH and low haptoglobin with indirect hyperbilirubinaemia — and then localised by one decisive test: the direct antiglobulin (Coombs) test. A positive DAT means immune haemolysis (warm IgG, cold IgM or drug-induced); a negative DAT with a suggestive smear means an inherited red cell defect — spherocytes point to hereditary spherocytosis, bite cells to G6PD deficiency, and periodic dark urine to paroxysmal nocturnal haemoglobinuria, confirmed on flow cytometry for CD55/CD59 with FLAER. In the Indian setting, G6PD deficiency matters beyond haematology: national malaria guidance requires G6PD testing before primaquine radical cure of vivax malaria.
What you must remember
- Screening triad: LDH raised (often above 600 U/L), haptoglobin undetectable, reticulocytes above 2–3% corrected, with indirect bilirubin and urinary urobilinogen raised.
- Intravascular markers — haemoglobinuria, haemosaiderinuria and low plasma haptoglobin — point to G6PD crises, mismatched transfusion, PNH or mechanical valves.
- DAT decides the first fork: IgG with or without complement in warm autoimmune haemolytic anaemia (spherocytes, steroids first-line); complement C3d alone in cold agglutinin disease (acral cyanosis, IgM with high thermal amplitude, treat by keeping warm and with rituximab).
- Donath-Landsteiner antibody causes paroxysmal cold haemoglobinuria — complement-mediated, classically in children after viral infection or syphilis.
- Hereditary spherocytosis: EMA binding by flow cytometry or osmotic fragility confirms; family history and pigment gallstones support; splenectomy helps but requires vaccination beforehand.
- G6PD deficiency: bite and blister cells during crisis, triggered by primaquine, dapsone, naphthalene or infection; assay is falsely normal during acute haemolysis or after transfusion because reticulocytes and donor cells are enzyme-rich.
- PNH screen: FLAER-based flow cytometry on granulocytes — pursue any Coombs-negative haemolysis with cytopenia, thrombosis or abdominal pain; eculizumab or ravulizumab for classical PNH.
- Secondary causes to close the file: systemic lupus erythematosus, chronic lymphocytic leukaemia, drugs (methyldopa, fludarabine), and Evans syndrome when immune thrombocytopenia joins AIHA.
How to work through suspected haemolysis
Begin with confirmation in a 24-year-old with jaundice and Hb 7.4 g/dL: reticulocytes 9%, LDH 950 U/L, haptoglobin less than 10 mg/dL, indirect bilirubin 3.2 mg/dL. Step two, the smear at the same visit — numerous spherocytes here, no fragments. Step three, the DAT: positive with IgG and complement — warm autoimmune haemolytic anaemia. Step four, hunt the driver: a full autoimmune screen (ANA, anti-dsDNA), a lymphocyte screen (CLL can present through its autoimmune complications), and a drug history, because methyldopa and fludarabine are classic exam triggers. Step five, treat in sequence — prednisolone 1 mg/kg for a response in one to three weeks, transfuse only when tolerated poorly (and expect crossmatch difficulty, since the antibody pan-reacts), then rituximab or splenectomy for steroid dependence.
Now vary one detail and the pathway forks: the same patient with a DAT negative, acral colour change in winter and a monospot-negative titre positive at 4 degrees Celsius has cold agglutinin disease — keep him warm, avoid steroids, and reach for rituximab, with underlying mycoplasma or lymphoma in mind. Change the smear to bite cells with a crisis after an antimalarial, and the diagnosis is G6PD deficiency — support with transfusion, stop the drug, and assay the enzyme weeks later, because assaying during the crisis reads falsely normal. Exchange the urine story for morning haemoglobinuria with a history of mesenteric vein thrombosis, and FLAER flow cytometry takes over from the DAT entirely.
The trap the examiner sets
The favourite stem gives a normal or high haptoglobin and expects you to know haptoglobin rises with inflammation and oestrogen, so it must fall for the right reasons as well as rise for the wrong ones. The second trap is timing the G6PD assay during acute haemolysis — the young enzyme-rich reticulocytes normalise the result, and the examiner will offer that false-normal number as a distractor. Third, spherocytes appear in both hereditary spherocytosis and warm AIHA; the DAT, not the shape, separates them — inherited disease in a DAT-negative patient, confirmed by EMA binding.
Frequently asked questions
Which three tests screen for haemolysis most reliably?
Reticulocyte count, LDH and haptoglobin, supported by indirect bilirubin — the pattern of all three localises the process within minutes.
What does a positive DAT with IgG indicate?
Warm autoimmune haemolytic anaemia — spherocytes on the smear, first-line prednisolone, with rituximab or splenectomy for refractory disease.
When is a G6PD assay unreliable?
During acute haemolysis or soon after transfusion, because surviving cells are enzyme-rich; repeat several weeks after the crisis.
How is paroxysmal nocturnal haemoglobinuria confirmed?
FLAER-based flow cytometry showing loss of glycosylphosphatidylinositol-anchored proteins (CD55/CD59) on granulocytes.
Why does cold agglutinin disease not respond to steroids?
The IgM antibody fixes complement at cooler temperatures and is largely intravascular; management is warmth, rituximab and treatment of the underlying lymphoproliferative or mycoplasma trigger.
Which Indian programme detail involves G6PD testing?
National malaria guidance requires documenting normal G6PD status before primaquine radical cure of Plasmodium vivax, since the drug can precipitate severe haemolysis.