The urgency with which anaemia is evaluated depends on the severity at presentation and whether the patient has active or acute bleeding.
Patients with active or acute bleeding
Evaluation should include identification of any source of active or acute bleeding.
The initial goal in a patient with acute bleeding is rapid haemodynamic stabilisation. Up to 30% of total blood volume (TBV) may be lost before clinical manifestations are appreciated at rest.
Patients with an acute severe haemorrhage present with symptoms and signs of hypovolaemia and the underlying cause.
Key signs of hypovolaemia include hypotension, pallor, cold clammy skin, thready pulse, tachycardia, dyspnoea and altered mental status. Flat neck veins when supine indicate at least 30% to 40% total body volume loss. All orifices should be examined for bleeding.
History of prior episodes of gastrointestinal (GI) bleeding, gastritis, inflammatory bowel disease, non-steroidal anti-inflammatory drug (NSAID) or corticosteroid use, alcohol use, or cirrhosis should prompt suspicion of GI bleeding. NSAIDs and corticosteroids are associated with peptic ulcer disease. Alcohol use and cirrhosis are associated with coagulation disorders and oesophageal varices. A lower GI bleed presents with fresh red rectal bleeding (haematochezia). Melaena and/or haematemesis with or without abdominal pain indicate an upper GI bleed.
Sudden tearing pain should prompt suspicion of a ruptured vascular aneurysm; the pain may be spontaneous, or precipitated by trauma or by cocaine or amphetamine use. Loss of consciousness may occur if a major vessel is involved. A history of hypertension or collagen disorders may also be present. A wide pulse pressure suggests a ruptured aneurysm. A pulsatile abdominal mass may indicate an abdominal aortic aneurysm. Flank or abdominal ecchymosis suggests intra-abdominal bleeding.
The mechanism and site of any trauma should be determined.
If there is a history of recent surgery, ongoing blood loss at the surgical site must be considered. A detailed history of the pre-, intra-, and postoperative course should be obtained, including any complications noted during the operation. Any antibiotics administered should be noted, as some can produce a decrease in platelet levels.
A history of bleeding disorders or excessive bruising may indicate an underlying coagulation disorder.
Jaundice, especially accompanied by fatigue and pallor, with episodic dark urine suggests a haemolytic process, especially with recent infection, new medications, or history of malignancy.
Tests are guided by the history and examination and the suspected aetiology of active bleeding. These may include the following procedures.
FBC, which shows a normocytic anaemia with a high reticulocyte count (>2%) and a normal or decreased haematocrit (Hct). Dilution does not occur initially, so haemoglobin (Hb) and Hct do not accurately reflect the true severity of the anaemia.
Prothrombin time/activated partial prothrombin time, which is usually normal, but tested to identify patients with decreased coagulation due to anticoagulants, underlying defects in haemostasis, or consumptive coagulopathy. In patients with upper GI bleeding, elevated urea may be seen, even in the absence of renal impairment, due to digestion of blood, which is a source of urea.
Abdominal ultrasound scan: allows rapid identification of intra-abdominal bleeding and indicated if abdominal trauma or a ruptured abdominal aortic aneurysm are suspected.
Joint x-rays, indicated in patients with trauma to identify fractures. Long-bone fractures can be a significant source of bleeding.
Computed tomography (CT) scanning of the body region affected by trauma or aneurysm rupture, which will identify internal injuries or the extent and the nature of the aneurysm, and identify sources of bleeding.
Colonoscopy, required to identify sources of lower GI bleeding.
Capsule endoscopy may have diagnostic, but not therapeutic, utility in situations where there is concern for GI bleeding in inaccessible areas such as the small bowel.
Exploratory laparotomy, which may be required in patients with abdominal bleeding to identify the source, especially if there is a history of abdominal trauma or previous abdominal surgery.
Patients without active or acute bleeding
Many anaemic patients with no acute or active bleeding are asymptomatic, and the anaemia is only noted on an FBC taken as part of the assessment of an unrelated condition. The duration of anaemia must be investigated, if possible.
Generally, healthy individuals tolerate extreme anaemia well, with cardiovascular status being the major limiting factor.
Symptoms of anaemia may include fatigue, weakness, decreased exercise tolerance, shortness of breath with exercise, palpitations, dizziness, irritability and impaired concentration.
There is a strong relationship between pica (a medical disorder in which children develop an appetite for non-nutritive substances) and iron deficiency.
Pallor is the most common sign in patients with anaemia. Jaundice is an additional sign seen in patients with haemolytic anaemias.
The first step in diagnosis is to identify the type of anaemia that is present, using the results of the FBC. Due to their relative reproducibility, mean corpuscular volume (MCV) and red cell width (RDW) are the most useful components in the initial classification of most anaemias.
The anaemia may be:
Microcytic (MCV <80 femtolitres [fL]): serum iron studies should be performed.
Normocytic (MCV 80-100 femtolitres [fL]): the reticulocyte count should be examined to determine whether the anaemia is hypoproliferative (<2%) or hyperproliferative (>2%).
Macrocytic (MCV >100 femtolitres [fL]): the peripheral smear should be examined for megaloblasts and hypersegmented neutrophils. If these cells are present, the anaemia is megaloblastic. If they are absent, the anaemia is non-megaloblastic.
Microcytic anaemia: abnormal serum iron studies
A low serum iron, an elevated total iron-binding capacity (TIBC), and a low ferritin indicate iron deficiency anaemia. Serum ferritin is the most sensitive and specific test for iron deficiency.
Iron deficiency produces an associated reactive thrombocytosis that provides an additional clue.
Iron deficiency is not a diagnosis and requires further investigation to elucidate the cause.
Associated symptoms may indicate a source of chronic bleeding e.g., heavy menstrual bleeding, coffee-ground vomiting, haematemesis, melena, rectal pain or rectal bleeding. Haemoptysis may indicate Goodpasture's syndrome or idiopathic pulmonary haemosiderosis. A history of dark-colored urine may indicate paroxysmal nocturnal haemoglobinuria.
Enquire about the patient's diet. Diets low in meat may produce iron deficiency. Generalised malnutrition often produces combined vitamin B12 and/or folate deficiency, in which case the resulting anaemia is normocytic. Children may have pica.
Alcohol use and cirrhosis are associated with coagulation disorders and oesophageal varices.
Rarely, a history of excessive blood donation or self-harm may be elicited. Patients who are avid runners may have runner's anaemia from repetitive mechanical trauma (also known as march haematuria). A history of gastric surgery, coeliac disease, or extensive small bowel resection suggests malabsorption as the cause. Pregnancy is a common cause of iron deficiency.
Signs of iron deficiency include koilonychia, angular cheilosis, glossitis, and thinning hair. Peripheral blood smear may show pencil cells.
Investigations are guided by the history and examination, and include the following.
Faecal occult blood testing, which should be done in all patients and is positive if GI bleeding is present. In the UK, the National Institute for Health and Care Excellence recommends faecal occult blood testing for adults who are aged ≥50 years and have unexplained changes in bowel habit or iron deficiency anaemia and adults aged ≥60 who have anaemia, even in the absence of iron deficiency.
Upper GI endoscopy, which should be performed if there is a history of upper GI bleeding or a positive faecal occult blood test. It may identify sources of an upper GI bleed (peptic ulcer disease, gastritis, oesophageal varices), hiatus hernia, Meckel's diverticulum, or increased gastric pH in achlorhydria.
Following negative endoscopy in the setting of persistent iron deficiency anaemia, testing for Helicobacter pylori may be considered.
Immunoglobulin A-tissue transglutaminase (IgA-tTG) test should be performed in all patients and is positive in coeliac disease.
Colonoscopy, which should be performed if there is a history of lower GI bleeding or a positive faecal occult blood test. It may reveal malignancy, diverticular disease, ulcerative colitis, or rare causes such as hereditary haemorrhagic telangiectasia. Malignancy should be considered in all patients aged over 40 years with symptoms of rectal bleeding or a positive faecal occult blood test. A retrospective review of the medical records of a sample of patients with colorectal cancer found that anaemia was one of the commonest signs in those considered to have had a missed diagnostic opportunity (a clinical encounter where, even in the presence of presumptive symptoms of colorectal cancer, the diagnostic process was not started). In the UK, the National Institute for Health and Care Excellence recommends that adults aged over 60 who have iron-deficiency anaemia should be referred urgently for investigation for colorectal cancer.
Flow cytometry should be considered if there is a history of passing red urine, or RBC results consistent with a haemolytic anaemia. It detects decreased expression of RBC surface proteins (CD55 and CD59) and is diagnostic of paroxysmal nocturnal haemoglobinuria.
Transvaginal ultrasound, which may reveal causes of menorrhagia including hyperplasia, dysplasia, fibroids, polyps or malignancy.
Stool microscopy, which may identify hookworm, whipworm, or Schistosoma eggs. This should be performed if clinical features suggest the diagnosis or there is a history of travel to endemic areas.
A low serum iron, a low total iron-binding capacity, and a low/normal ferritin suggest co-existence of anaemia of chronic disease with iron deficiency.
A history of an underlying inflammatory process (infection, neoplasms, autoimmune reactions, and injury to tissue from trauma or major surgery) is usually present. Serum C-reactive protein may be raised.
A serum erythropoietin level should be considered; the result is usually normal or mildly elevated. Ferritin is an acute phase protein and serum levels can rise in inflammatory conditions, liver disease and malignancy, even though iron stores are low. Hypothyroidism and vitamin C deficiency may produce a falsely low ferritin level.
Microcytic anaemia: normal serum iron studies
The most important cause to exclude is thalassaemia. A family history is usually present. The disease is more common in individuals of Mediterranean, Middle Eastern, or Southeast Asian descent.
The examination findings may be normal, or reveal splenomegaly, jaundice, abdominal distension, and icterus. Morphological changes including skeletal abnormalities, a large head, chipmunk facies, and misaligned teeth are seen in beta-thalassaemia intermedia and major.
Distinct features on the FBC that suggest the diagnosis include a marked decrease in MCV (usually close to 70 femtolitres [fL]) with a low mean corpuscular Hb, target cells on the peripheral smear, and an elevated reticulocyte count (>2%). A Mentzer's index (MCV/RBC) <13 is suggestive of thalassaemia, and an index >14 suggests iron deficiency. In a meta-analysis of various mathematical indices used to distinguish between iron deficiency anaemia and thalassaemias, the microcytic to hypochromic RBC ratio (M/H) showed the best performance, although the authors concluded that none were high enough to make definitive diagnoses.
Thalassaemia is diagnosed using Hb electrophoresis. The presence of Hb H, Hb Bart, and concomitant haemoglobinopathies (Hb E, Hb S, Hb C, Hb D) is diagnostic of alpha-thalassaemia. A high HbF with minimal or absent HbA and an elevated HbA2 is diagnostic of beta-thalassaemia.
Normocytic anaemia: hypoproliferative
Haematological malignancies and aplastic anaemia are the most important diagnoses to exclude, and are usually associated with multiple cytopenias. An isolated anaemia is usually due to pure red cell aplasia. Chronic kidney disease or hypothyroidism can also cause an isolated anaemia.
Symptoms of bleeding, easy bruising, night sweats, or weight loss suggest haematological malignancy or aplastic anaemia. Enquire about symptoms and risk factors for infections which can cause self-limiting pure red cell aplasia, such as parvovirus infection, infectious mononucleosis, viral hepatitis, malaria, respiratory infections, gastroenteritis and mumps.
Medication: Phenytoin, carbamazepine, sodium valproate, azathioprine, sulfonamides, isoniazid and procainamide cause pure red cell aplasia. Benzene, penicillamine, and gold can cause aplastic anaemia. Chloramphenicol can cause either aplastic anaemia or pure red cell aplasia. Chemotherapy causes pancytopenia.
Radiotherapy, especially to pelvic or sternal areas, can cause pancytopenia.
A history of autoimmune disease or chronic hepatitis suggests persistent pure red cell aplasia.
There may be a history or features of chronic kidney disease or hypothyroidism.
Ecchymoses or petechiae due to thrombocytopenia suggest haematological malignancy, myelodysplastic syndrome, or aplastic anaemia. Lymphadenopathy or fever suggest malignancy or infections. Splenomegaly may be seen in haematological malignancies.
Should be guided by the history and examination findings.
FBC may show an associated cytopenia and characteristic changes specific to a haematological malignancy. A pancytopenia suggests aplastic anaemia, or may be due to chemotherapy or radiotherapy. An isolated anaemia suggests pure red cell aplasia or anaemia due to chronic kidney disease.
Bone marrow biopsy is required for the definitive diagnosis of acute leukaemia (acute lymphocytic leukaemia, acute myelogenous leukaemia), chronic myelogenous leukaemia (CML), aplastic anaemia, or bone marrow metastases.
Antiparvovirus antibodies are positive in parvovirus infection, the most common infectious cause of pure red cell aplasia.
Other tests to consider
Hepatitis serology, to exclude acute or chronic active hepatitis
Monospot test (heterophile antibodies) or Epstein-Barr virus-specific antibodies to exclude infectious mononucleosis. Viral capsid antigen-IgM (VCA-IgM) is detectable in most patients with symptom onset
Thick and thin peripheral smear, to exclude malaria if history and clinical findings suggest the diagnosis
Thyroid function tests; thyroid-stimulating hormone (TSH) is elevated and free thyroxine (T4) reduced in hypothyroidism
Antinuclear antibodies, which are positive in systemic lupus erythematosus or scleroderma
Rheumatoid factor, which may be positive in rheumatoid arthritis
Serum creatine kinase (CK), which is elevated in dermatomyositis
Erythropoietin levels, which may be inappropriately decreased in patients with chronic renal failure. Serum calcium and parathyroid hormone levels should be considered if associated secondary hyperparathyroidism is suspected
Chest x-ray, which may show infiltrates in atypical pneumonia or a smooth mass in thymoma.
Normocytic anaemia: hyperproliferative
Potential diagnoses include haemorrhage and haemolytic anaemias.
Drugs that can cause haemolysis include penicillin, methyldopa, levodopa, quinidines, cephalosporins, and some NSAIDs. Cyclosporine, tacrolimus, clopidogrel, oral contraceptive pills, and some chemotherapy drugs may cause haemolytic uraemic syndrome.
There may be a history suggestive of microangiopathic disease. Known triggers of disseminated intravascular coagulation (DIC) include ongoing severe infection, sepsis, malignancy, obstetric emergency, trauma, burns, pancreatitis, liver failure, envenomation, drug overdose, or any cause of endothelial damage.
The presence of acute-onset neurological symptoms, including headache, confusion, focal weakness, seizures, or coma, should prompt suspicion of thrombotic thrombocytopenic purpura (TTP). Female patients may have associated menorrhagia.
Sudden-onset dizziness, headache, mental status changes, loss of sensation or motor strength, chest pain or pressure, dyspnoea, or oedema in a patient with known hypertension should prompt suspicion of malignant hypertension; a history of renal failure or eclampsia may also be present.
An expanding vascular skin lesion in a young infant or child should prompt suspicion of a haemangioma.
A history of prosthetic valve replacement may indicate haemolysis induced by the prosthesis.
Bloody diarrhoea should prompt suspicion of Escherichia coli infection and haemolytic uraemic syndrome.
Persistent pain in the skeleton, chest, or abdomen; priapism; lower-extremity skin ulcers; or an acute pneumonia-like syndrome suggest sickle cell anaemia.
Patients with inherited haemolytic anaemias such as sickle cell anaemia, hereditary spherocytosis, or glucose-6-phosphate dehydrogenase (G6PD) deficiency may have a positive family history.
There may be a previous history of autoimmune disease (e.g., systemic lupus erythematosus, rheumatoid arthritis, or scleroderma) or lymphoproliferative disorders (usually non-Hodgkin's lymphoma or chronic lymphocytic leukaemia), which can lead to autoimmune haemolytic anaemia. Note that autoimmune diseases may also cause pure red cell aplasia, in which case the reticulocyte count would be low, with normal lactate dehydrogenase, haptoglobin, and bilirubin levels.
Recent blood transfusion may indicate haemolysis due to a transfusion reaction.
Occupational or home exposure to lead should prompt suspicion of lead toxicity.
Features of microangiopathic disease: there may be purpura or ecchymoses due to bleeding. Systolic BP >210 mmHg and diastolic BP >130 mmHg indicate malignant hypertension; associated signs may include new murmurs, S3 on auscultation of the heart, jugular venous distension, rales or lower-extremity oedema, oliguria or polyuria, focal neurological signs, and hypertensive retinopathy. Cutaneous reddish-brown or violaceous vascular lesions may indicate haemangioma.
Splenomegaly is seen in hereditary spherocytosis. Clinical features of underlying autoimmune diseases may be present. Lymphadenopathy may indicate infectious mononucleosis, leukaemia, lymphoma, or autoimmune disease.
The FBC and peripheral blood smear should be examined for clues to the underlying cause. A thrombocytopenia with schistocytes strongly suggests a microangiopathic haemolytic anaemia. Spherocytes suggest autoimmune haemolytic anaemia or hereditary spherocytosis. Hereditary spherocytosis is also associated with increased mean corpuscular Hb. Sickling of RBCs is diagnostic of sickle cell anaemia. Heinz bodies, eccentrocytes, or bite cells are seen in G6PD deficiency.
If haemolytic anaemia is suspected, serum lactate dehydrogenase, haptoglobin, and bilirubin should be measured. Elevated lactate dehydrogenase and bilirubin levels with a decreased haptoglobin are strongly suggestive of a haemolytic anaemia. Clinical jaundice is seen once bilirubin levels rise above 34.2 to 68.4 mmol/L (2-4 mg/dL).
Tests to consider in suspected microangiopathic haemolytic anaemias
Serum creatinine, which may be elevated in patients with haemolytic uraemic syndrome or malignant hypertension.
Urine dipstick, which may show haematuria and/or proteinuria in haemolytic uraemic syndrome
Stool tests: culture, polymerase chain reaction for enterohaemorrhagic E. coli genes, or enzyme-linked immunosorbent assay for Shiga toxin in haemolytic uraemic syndrome.
Prothrombin time and activated partial prothrombin time, which are prolonged in DIC but normal in other microangiopathic haemolytic anaemias.
DIC panel shows elevated D-dimers and fibrin degradation products with low fibrinogen in patients with DIC.
X-rays and magnetic resonance imaging (MRI) scanning of suspected regions reveal internal haemangiomas.
Tests to consider in other haemolytic anaemias
Direct antiglobulin (Coombs') test, which is positive in autoimmune haemolytic anaemia.
Tests to identify hereditary causes. Sickle cell anaemia is diagnosed on FBC. Osmotic fragility test is positive in hereditary spherocytosis; cells lyse on exposure to hypo-osmotic solution. G6PD assays identify deficiencies of the enzyme.
Tests to identify infection. Monospot test or viral capsid antigen IgM is positive in infectious mononucleosis. CMV IgM is positive in CMV infection. Double-sandwich IgM enzyme-linked immunosorbent assay (ELISA) or IgG avidity test is positive for IgM in acute toxoplasmosis. Splenic or bone marrow aspirate shows amastigotes of the parasite in leishmaniasis.
Blood lead levels, which are elevated in lead toxicity.
Venepuncture and phlebotomy animated demonstration
Macrocytic anaemia: megaloblastic
The main causes to consider are vitamin B12 or folate deficiency, or drugs that interfere with DNA synthesis. Autoimmune thyroid disease may coexist with pernicious anaemia and atrophic gastritis, which decrease B12 absorption. Therefore, screening for B12 deficiency when the aetiology of hypothyroidism is thought to be autoimmune is recommended.
Poor intake due to malnutrition, alcohol abuse, or strict vegan or low-protein diets can produce deficiency of vitamin B12 and/or folate.
A history of coeliac disease, tropical sprue, Crohn's disease, previous gastric or intestinal surgery, or bacterial overgrowth may indicate malabsorption.
A swollen, red, painful tongue; angular stomatitis; patchy hyperpigmentation of the skin and mucous membranes; and a persistent mild pyrexia are symptoms of folate deficiency.
Drug history: known causative medications include purine analogues, pyrimidine analogues, reductase inhibitors, methotrexate, trimethoprim, anticonvulsants, oral contraceptives, cycloserine, p-aminosalicylic acid, metformin, colchicine, neomycin, and biguanides. Hydroxyurea, in particular, is known to cause oval macrocytosis with MCV >110 femtolitres (fL).
Serum vitamin B12 levels are decreased and serum methylmalonic acid levels are elevated in vitamin B12 deficiency. The latter is more sensitive and should be used to definitively exclude vitamin B12 deficiency. An MCV of >115 fL is typically seen in nutritional deficiency.
Serum folate levels are low in folate deficiency. If folate levels are low, serum vitamin B12 and methylmalonic acid levels should be measured to exclude concurrent vitamin B12 deficiency before folate levels are corrected. Normal serum homocysteine levels make folate deficiency unlikely. RBC folate is a more accurate indicator of folate deficiency than serum folate level.
Anti-intrinsic factor and parietal cell antibodies are positive in pernicious anaemia.
Macrocytic anaemia: non-megaloblastic
Causes to consider include alcohol abuse, myelodysplastic syndrome, chronic liver disease, and congenital bone marrow failure syndromes.
High alcohol intake indicates alcohol-induced anaemia, which usually persists for months after total abstinence. A history of chronic liver disease indicates liver disease-induced anaemia.
History of prior exposure to petroleum distillates (especially benzene), chemotherapy, or radiotherapy should prompt suspicion of myelodysplastic syndrome.
A history of fever, chills, fatigue, weakness, recurrent infection, anorexia, night sweats, shortness of breath, and easy bruising should prompt suspicion of myelodysplastic syndrome.
Recurrent infections in an infant should prompt suspicion of congenital bone marrow failure syndromes.
May reveal stigmata of chronic alcoholism or chronic liver disease.
Pallor, petechiae and purpura may be present in myelodysplastic syndrome.
Dyskeratosis congenita is characterised by the triad of abnormal nails, reticulated skin rash, and leukoplakia.
Skeletal abnormalities and growth retardation are seen in Shwachman-Diamond syndrome.
FBC shows associated neutropenia and thrombocytopenia with macro-ovalocytes in myelodysplastic syndrome.
Bone marrow aspiration and biopsy shows myeloblasts with immature precursors in myelodysplastic syndrome. Diagnostic features of congenital bone marrow failure syndromes are also identified.
Cytogenetics reveal chromosomal translocations in myelodysplastic syndrome.
Additional tests for congenital bone marrow syndromes: diepoxybutane or mitomycin-c fragility test is positive in Fanconi anaemia. Genetic testing reveals underlying mutations.
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