Synopsis
Confirm accelerated red-cell destruction, separate intravascular from extravascular and immune from non-immune mechanisms, and recognise fragmentation, transfusion reactions and inherited disorders requiring urgent action.
- Confirm haemolysis with a pattern, not a solitary LDH: falling haemoglobin, raised absolute reticulocytes, unconjugated bilirubin and LDH, reduced haptoglobin and supportive film findings should be reconciled with timing and liver function.
- A low reticulocyte response does not exclude dangerous haemolysis early in the episode or when infection, marrow disease, renal failure, iron, B12 or folate deficiency limits compensation.
- The direct antiglobulin test detects immunoglobulin or complement on red cells; it supports immune classification but does not by itself prove that active haemolysis is occurring.
- Schistocytes with thrombocytopenia and organ injury raise thrombotic microangiopathy, disseminated coagulation or mechanical fragmentation and demand urgent clinical context rather than a routine outpatient haemolysis screen.
- Spherocytes occur in warm immune haemolysis and hereditary spherocytosis. DAT, family history, MCHC, splenomegaly and specialist membrane testing distinguish them.
- Separate intravascular clues, such as haemoglobinaemia, haemoglobinuria, very low haptoglobin and renal injury, from extravascular jaundice, splenomegaly and macrophage-mediated clearance; overlap is common.
- Always review recent transfusion, pregnancy, medicines, infection, travel, prosthetic valves, burns, family and ethnic background and episodic triggers before selecting specialised tests.
- G6PD activity can be falsely reassuring during or soon after an acute episode because older deficient cells have been destroyed and transfused or reticulocyte-rich blood is over-represented; repeat later if suspicion remains.
Key red flags
Dark urine, haemoglobinaemia or haemoglobinuria, markedly consumed haptoglobin, renal injury and rapid symptoms indicate free haemoglobin released within the circulation.
Schistocytes, thrombocytopenia, neurological, renal, cardiac or gastrointestinal injury and biochemical haemolysis requires urgent TTP and secondary-microangiopathy assessment.
Fever, chills, pain, dyspnoea, hypotension, dark urine or unexpected haemoglobin fall during or after transfusion requires immediate transfusion-reaction management.
Investigation priorities
Quantify anaemia, compensation and tempo across all lineages.
Management branches
There is shock, severe symptomatic anaemia, haemoglobinuria with kidney injury, thrombocytopenia with fragments, or a suspected transfusion reaction.
- Use ABCDE, stop any transfusion, maintain venous access, check identity and send urgent FBC, film, reticulocytes, haemolysis, renal, coagulation, group and blood-bank reaction samples while supporting circulation and urine output.
- The preferred emergency route is immediate senior haematology and transfusion discussion, with a TTP pathway for high-probability microangiopathy and the local transfusion-reaction pathway for temporally related haemolysis.
- Escalate neurological, renal, cardiac or respiratory compromise to critical care and give compatible red cells for threatened oxygen delivery without waiting for every specialised result.
Anaemia, jaundice, reticulocytosis, dark urine or an abnormal film raises red-cell destruction in a stable patient.
- First-line tests are FBC, absolute reticulocytes, film, bilirubin, LDH, haptoglobin, DAT, renal and liver profile, urinalysis and a careful transfusion, medicine, infection and family history.
- Classify intravascular versus extravascular and immune versus non-immune using DAT and morphology; an alternative diagnosis is ineffective B12 or folate erythropoiesis when LDH is high but reticulocytes remain low.