Phys · haematological
Anaemia — Systematic Workup
Also known as anaemia investigation · low haemoglobin workup · microcytic anaemia · macrocytic anaemia · normocytic anaemia · iron deficiency anaemia · IDA · pernicious anaemia · vitamin B12 deficiency · folate deficiency · haemolytic anaemia · autoimmune haemolytic anaemia · AIHA · hereditary spherocytosis · G6PD deficiency · thalassaemia trait · anaemia of chronic disease · aplastic anaemia · reticulocyte count · iron studies · transfusion threshold · direct antiglobulin test · DAT · Coombs test
Consultant-physician-depth guide to the systematic investigation of anaemia. Covers MCV-based classification (microcytic, normocytic, macrocytic), the reticulocyte count as kinetic discriminator, iron-studies interpretation, the iron deficiency workup in adults (mandatory GI source search), haemolytic anaemia classification, blood-film morphology, transfusion thresholds, and the management of each major cause. Structured for FRACP DWE and DCE preparation.
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Target exams
Red flags
- Hb < 70 g/L in a stable adult, or any Hb with haemodynamic instability — assess for transfusion
- Anaemia with chest pain, ischaemic ECG changes, or new heart failure — transfuse to keep Hb above 80 g/L
- Pancytopenia on FBC — marrow failure, aplastic anaemia, acute leukaemia, or megaloblastic anaemia; urgent blood film and marrow biopsy
- B12 deficiency treated with folate alone — risk of precipitating subacute combined degeneration of the spinal cord
- Iron deficiency anaemia in a man or postmenopausal woman — always investigate for GI malignancy unless an obvious other cause is found
- Acute haemolysis with falling Hb and rising LDH — immune, drug-induced or microangiopathic; urgent DAT, blood film and haemostasis screen
- Methylene blue must not be given to a patient with suspected G6PD deficiency — it is an oxidant and worsens haemolysis
Anaemia — Systematic Workup
The answer first
Anaemia is investigated by a reproducible, two-axis system: the morphological axis (the mean cell volume — microcytic, normocytic, macrocytic) and the kinetic axis (the reticulocyte count — is the marrow responding or not). The registrar who applies these two axes to every low haemoglobin will reach the cause; the one who chases a scatter of tests will miss the GI cancer hiding behind a "simple" iron deficiency. [1]
The mandate in three steps: [1]
- Confirm anaemia and classify by MCV. Take a full blood count and look at the MCV. Is the cell small, normal or large? This is the first branch point.
- Apply the reticulocyte count as the kinetic discriminator. Is the marrow trying to replace the lost cells (reticulocytes high — think haemolysis or bleeding or recovery) or failing to produce them (reticulocytes low — think iron/B12/folate deficiency, marrow failure, chronic disease)?
- Target the cause with the right panel. Iron studies for the microcytic anaemias; B12 and folate for macrocytosis; DAT, LDH and haptoglobin for haemolysis; a blood film for morphology; and a bone marrow biopsy when the marrow itself is suspect. [1]
The single most important principle for the exam: never treat anaemia as the diagnosis. Anaemia is a sign. Iron deficiency anaemia in a man or a postmenopausal woman is GI malignancy until proven otherwise — the iron studies confirm the deficiency, but the endoscopy and colonoscopy find the cause [1].
References8ShowHide
- [1]Goddard AF, James MW, McIntyre AS, Scott BB Guidelines for the management of iron deficiency anaemia Gut, 2011.PMID 21561874
- [2]Stabler SP Clinical practice. Vitamin B12 deficiency N Engl J Med, 2013.PMID 23301732
- [3]Hébert PC, Wells G, Blajchman MA, et al. A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. Transfusion Requirements in Critical Care Investigators, Canadian Critical Care Trials Group N Engl J Med, 1999.PMID 9971864
- [4]Carson JL, Terrin ML, Noveck H, et al. Liberal or restrictive transfusion in high-risk patients after hip surgery N Engl J Med, 2011.PMID 22168590
- [5]Carson JL, Grossman BJ, Kleinman S, et al. Red blood cell transfusion: a clinical practice guideline from the AABB* Ann Intern Med, 2012.PMID 22751760
- [6]Jäger U, Barcellini W, Broome CM, et al. Diagnosis and treatment of autoimmune hemolytic anemia in adults: Recommendations from the First International Consensus Meeting Blood Rev, 2020.PMID 31839434
- [7]Luzzatto L, Ally M, Notaro R Glucose-6-phosphate dehydrogenase deficiency Blood, 2020.PMID 32702756
- [8]Manciu S, Matei E, Trandafir B Hereditary Spherocytosis - Diagnosis, Surgical Treatment and Outcomes. A Literature Review Chirurgia (Bucur), 2017.PMID 28463670