AKT · Haematology/Anaemia & red cell

Abnormal blood film

Morphological abnormality of red cells, white cells or platelets

Overview

The blood film is where a numerical abnormality becomes a diagnosis. Recognising a handful of morphologies — and knowing which of them demand a phone call the same day — is the practical skill being tested.

Recognise

BLASTS → acute leukaemia. This is a same-day haematology call, not a routine referral
Schistocytes (red cell fragments) → microangiopathic haemolysis: TTP, HUS or DIC
Spherocytes → hereditary spherocytosis or autoimmune haemolysis (a positive direct antiglobulin test separates them)
Howell–Jolly bodies → hyposplenism or post-splenectomy; the patient needs vaccination and antibiotic prophylaxis
Target cells → liver disease, thalassaemia, iron deficiency, hyposplenism
Tear-drop poikilocytes with a leucoerythroblastic film → myelofibrosis or marrow infiltration
Rouleaux with a high ESR → myeloma
Smear/smudge cells → chronic lymphocytic leukaemia
Hypersegmented neutrophils → B12 or folate deficiency

Red flags

Blasts, or schistocytes with thrombocytopenia → discuss with haematology the same day; untreated TTP and acute leukaemia both kill within days

Differentials & how to tell them apart

TTPSchistocytes with severe thrombocytopenia, fever, renal impairment and neurological signs — NORMAL clotting, unlike DIC

DICSchistocytes WITH deranged clotting, low fibrinogen and raised D-dimer in a septic or obstetric patient

Acute leukaemiaBlasts on the film with pancytopenia and marrow failure symptoms

CLLLymphocytosis with smear cells in an older, often asymptomatic patient

Megaloblastic anaemiaMacrocytosis with hypersegmented neutrophils and low B12 or folate

Leukaemoid reactionMarked neutrophilia with a left shift in severe infection — no blasts, and it resolves with the infection

Investigations

FBC with the film reported by a haematologist, plus reticulocytes, haematinics (ferritin, B12, folate), LDH, bilirubin and haptoglobin where haemolysis is suspected, a direct antiglobulin test, U&E, LFT, clotting and fibrinogen. Escalate to bone marrow aspirate/trephine, immunophenotyping or cytogenetics on haematology advice.

Management

Correlate the film with the counts and the clinical picture, and identify the urgent morphologies immediately

1Read the film alongside the full blood count and the patient. Ask three questions: are there blasts, are there schistocytes, and is more than one cell line affected?
2Urgent morphologies (blasts, schistocytes with thrombocytopenia) → same-day haematology discussion.Gate: Pancytopenia, blasts, or suspected TTP → emergency admission; TTP needs plasma exchange within hours
3Non-urgent findings: work up the cause with haematinics, liver and renal function, and repeat the film after treating the reversible causes.

Key points

The single most important discrimination is schistocytes with NORMAL clotting (think TTP — plasma exchange, and never give platelets) versus schistocytes with DERANGED clotting (think DIC — treat the underlying cause). Getting that the wrong way round is actively harmful.

Monitor & prognosis

Repeat FBC and film to track response; frequency set by the diagnosis.

Entirely dependent on the underlying cause, from an incidental hyposplenic film to acute leukaemia.

Source: British Society for Haematology guidelines · NICE NG12 (suspected cancer referral)