Synopsis
Use blood-film morphology to verify automated counts, recognise time-critical haematological patterns and direct confirmatory testing without turning a descriptive cell shape into a final diagnosis.
- Read the film alongside the full blood count, reticulocytes, clinical question and sampling history. Morphology without the numerical and clinical context is vulnerable to over-interpretation.
- Start at low power for distribution, rouleaux, agglutination, large abnormal cells and platelet clumps, then use higher power for red-cell shape, white-cell maturation, inclusions and platelet morphology.
- Schistocytes indicate mechanical fragmentation but are not synonymous with TTP; thrombocytopenia, haemolysis, renal, neurological and coagulation findings decide the thrombotic-microangiopathy or DIC pathway.
- Spherocytes support extravascular red-cell membrane loss and occur in warm autoimmune haemolysis and hereditary spherocytosis. The direct antiglobulin test and family or transfusion history discriminate.
- Target cells occur with haemoglobinopathy, liver disease, iron deficiency and hyposplenism; teardrops plus a leucoerythroblastic picture raise marrow fibrosis or infiltration but can have other causes.
- Blasts require urgent expert classification. Abnormal promyelocytes with bleeding or coagulation disturbance raises acute promyelocytic leukaemia, for which specialist treatment is time critical.
- Reactive lymphocytes can accompany viral infection, while a monotonous small-lymphocyte population suggests a clonal process. Flow cytometry answers lineage and clonality when indicated.
- A negative or non-specific film does not exclude serious disease. Early haemolysis, marrow disease and infection may need serial counts, biochemical tests, cultures, flow or marrow assessment.
Key red flags
Schistocytes with falling haemoglobin, thrombocytopenia, high LDH and low haptoglobin indicate fragmentation. Neurological, renal or cardiac involvement increases urgency for a thrombotic-microangiopathy pathway.
Circulating blasts, Auer rods or abnormal promyelocytes may accompany anaemia, thrombocytopenia and infection or bleeding. Prompt expert morphology, flow, genetics and coagulation assessment is required.
Malaria parasites or other visible organisms in a compatible traveller can establish an urgent infectious diagnosis, but species, parasitaemia and repeat sampling follow specialist protocols.
Investigation priorities
Confirm morphology, estimate abnormal-cell burden and issue time-critical alerts.
Management branches
Schistocytes accompany anaemia, thrombocytopenia or new renal, neurological, cardiac or bleeding features.
- Preferred first-line assessment is urgent repeat FBC, reticulocytes, LDH, bilirubin, haptoglobin, renal profile, urinalysis, coagulation, blood pressure and direct antiglobulin testing, with expert film confirmation.
- If TTP is plausible, send pre-plasma ADAMTS13 and escalate immediately to the regional TTP service; do not wait for a historical pentad or the activity result before specialist treatment decisions.
- Alternative causes include DIC, malignant hypertension, mechanical valves and severe burns; use coagulation, clinical context and organ pattern, escalating unresolved microangiopathic haemolysis to haematology.