The Full Blood Count
The full blood count provides information about a patient's red cells, white cells and platelets. This may be used for several purposing including diagnosing anaemia, monitoring infection or uncovering haematologic disorders.
Red Cell Count & Haemoglobin
The first step in the identification of red blood cell pathology is to look at the haemoglobin, haematocrit and red cell count. A reduction in each of these indices is used to diagnose anaemia, while an increase in these values is used to diagnose erythrocytosis.
|Ref Interval (Males)||Ref Interval (Females)|
|Hb||130 - 180 g/L||115 - 165 g/L|
|Hct / PCV||40 - 54%||36 - 44%|
Haemoglobin (Hb) is a protein within red blood cells which is composed of a haem molecule and four subunits. Haemoglobin transports oxygen and other molecules in blood. This is the most commonly used marker of anaemia.
The haematocrit (Hct), also known as the packed cell volume (PCV), is the volume of red blood cells as a percentage of total blood volume. This value is often calculated by an automatic analyser based on the red cell count and mean cell volume (MCV).
The red cell count reflects the number of circulating red blood cells. The red cell count is particularly useful in identifying erythrocytosis; a normal red cell count with elevated haemoglobin / haematocrit suggests relative erythrocytosis (e.g. dehydration), while an elevated red cell count suggests absolute erythrocytosis (e.g. polycythaemia vera).
Red Cell Size & Colour
Mean Cell Volume and Mean Corpuscular Haemoglobin
- These values are used to rapidly narrow down the likely causes of a patient’s anaemia, using a few specific patterns.
|MCV||80 - 100 fL|
|MCH||27 - 32 pg|
|MCHC||300 - 350 g/L|
The mean cell volume (MCV) is a measure of the average volume of a red blood cell - whether the cells are microcytic, normocytic or macrocytic.
The mean corpuscular haemoglobin (MCH) is the average amount of haemoglobin per red blood cell, while the mean corpuscular haemoglobin concentration (MCHC) refers to the average concentration of haemoglobin within red blood cells - these two measures are used to determine whether red cells are hypochromic or hyperchromic.
A microcytic, hypochromic anaemia contains predominantly small and pale cells. This is classically a sign of iron deficiency anaemia, however can also occur with thalassaemia, lead poisoning, congenital sidroblastic anaemia and hyperthyroidism.
A normocytic, normochromic anaemia is where the red blood cells are normal in size and colour. This may be dilutional or occur in the context of acute haemorrhage, chronic kidney disease, bone marrow pathology or haemolytic anaemia.
A macrocytic, hyperchromic anaemia refers to large red cells with loss of central pallor. This is classically a sign of megaloblastic anaemia (B12 / folate deficiency or drugs), though may also occur with myelodysplastic syndrome, alcohol abuse and severe hypothyroidism.
Red Cell Distribution Width
- Red cell distribution width (RDW) is the amount of variation in red blood cell size. Cells may be relatively uniform in size and have a low RDW, or have a wide range of sizes and have a high RDW.
An elevated RDW is referred to as anisocytosis, and indicates that red blood cells are a wide range of sizes. This can suggest a developing microcytic / macrocytic pathology such as early iron, B12 or folate deficiency; it may also be seen in haemolysis or following blood transfusion.
Reticulocytes are non-nucleated immature red blood cells. They are not normally present in the circulation in high numbers, though may be seen if the bone marrow is producing large numbers of red cells.
White Blood Cells
Leukocytes are a variety of cells of myeloid and lymphoid lineage that perform a variety of immune functions.
|WCC||Males: 3.7 - 9.5 x 10⁹/L|
Females: 3.9 - 11.1 x 10⁹/L
|Neutrophils||2.0 - 8.0 x 10⁹/L (40 - 75%)|
|Lymphocytes||1.0 - 4.0 x 10⁹/L (20 - 40%)|
|Monocytes||0.2 - 1.0; x 10⁹/L (2 - 8%)|
|Eosinophils||0.0 - 0.5 x 10⁹/L (1 - 4%)|
|Basophils||0.0 - 0.1 x 10⁹/L (0.5 - 1%)|
Leukocytosis refers to an increase in circulating white blood cells. This may be due to infection, inflammation, malignancy or certain other conditions. Leukopaenia refers to a reduction in circulating white blood cells; this is almost always caused by neutropaenia, lymphopaenia, or both.
- Neutrophils are are the most prevalent white blood cells in circulation.
An increase in neutrophils is known as neutrophilia. This is commonly caused by acute infection (particularly bacterial), though is also seen with inflammation, myeloproliferative neoplasms, corticosteroid administration and with heavy smoking. Pseudoneutrophilia is where there is shift of granulocytes into circulation without an increase in the total number of neutrophils - this can be seen in situations such as vigorous exercise and emotional stress.
A reduction in neutrophils is referred to as neutropaenia. This may be congenital or be acquired due to viral infection, autoimmune conditions, bone marrow pathology, dietary deficiency and certain drugs.
- Lymphocytes are small leukocytes that play several key roles in the adaptive immune response.
Lymphocytosis is an increase in circulating lymphocytes. This may occur in the context of acute viral infection, adrenocortical insufficiency, post splenectomy, chronic tuberculosis or chronic lymphocytic leukaemia (CLL).
Lymphopaenia refers to a reduction in the number of circulating lymphocytes. This is seen with primary immunodeficiency syndromes, certain infections, certain medications, bone marrow pathology and with dietary deficiency.
- Monocytes are large leukocytes of myeloid origin. An increase in circulating monocytes, or monocytosis, may occur with chronic infection, chronic inflammation, certain haematologic malignancies, or post splenectomy.
- The primary physiologic role of eosinophils is to defend against parasitic infection, though they also play an important role in the pathogenesis of allergy and certain other hypersensitivity reactions.
- Eosinophilia is an increase in eosinophils, which may be seen with:
- Allergies - such as asthma, allergic rhinitis or chronic sinusitis
- Drug reactions - whether allergic or other hypersensitivity reactions
- Parasitic infections - e.g. helminths or protozoa
- Eosinophilic granulomatosis with polyangiitis (Churg-Strauss)
- Eosinophilic leukaemia
- Basophils are uncommon white blood cells. Basophilia may be seen with viral infections, allergy, inflammation and certain haematologic malignancies.
Platelets are very small non-nucleated cells that derive from fragmentation of megakaryocytes. They play an important role in clot formation and haemostasis.
|Platelets||150 - 400 x 10⁹/L|
Thrombocytosis is an increase in circulating platelets. Primary thrombocytosis is seen with myeloproliferative neoplasms such as essential thrombocytosis or CML, while secondary thrombocytosis may occur in reaction to infection, inflammation or malignancy.
Thrombocytopaenia is a reduction in platelets. This may occur within the context of bone marrow failure, suppression or infiltration; dietary deficiency; splenomegaly (e.g. due to cirrhosis); viral infections and immune-mediated thrombocytopaenias (e.g. ITP, HIT, DIC, TTP, HUS). Thrombocytopaenia may also be congenital.
Abramson NE, Melton BE. Leukocytosis: basics of clinical assessment. American family physician. 2000 Nov 1;62(9):2053-66.Aslinia F, Mazza JJ, Yale SH. Megaloblastic anemia and other causes of macrocytosis. Clinical medicine & research. 2006 Sep 1;4(3):236-41.Brass D, Mckay P, Scott F. Investigating an incidental finding of lymphopenia. BMJ. 2014 Mar 3;348:g1721.
Brodsky RA, Jones RJ. Aplastic anaemia. The Lancet. 2005 May 7;365(9471):1647-56.
Buchanan GR, DeBaun MR, Quinn CT, Steinberg MH. Sickle cell disease. ASH Education program book. 2004;2004(1):35-47.
Bunn HF. Pathogenesis and treatment of sickle cell disease. New England Journal of Medicine. 1997 Sep 11;337(11):762-9.Capsoni F, Sarzi-Puttini P, Zanella A. Primary and secondary autoimmune neutropenia. Arthritis research & therapy. 2005 Aug 31;7(5):208.
Galanello R, Origa R. Beta-thalassemia. Orphanet journal of rare diseases. 2010 Dec 1;5(1):11.
Gayathri BN, Rao KS. Pancytopenia: a clinico hematological study. Journal of laboratory physicians. 2011 Jan;3(1):15.
George JN, Aster RH. Drug-induced thrombocytopenia: pathogenesis, evaluation, and management. ASH Education Program Book. 2009 Jan 1;2009(1):153-8.Gibson C, Berliner N. How we evaluate and treat neutropenia in adults. Blood. 2014 Aug 21;124(8):1251-8.Griesshammer M, Bangerter M, Sauer T, Wennauer R, Bergmann L, Heimpel H. Aetiology and clinical significance of thrombocytosis: analysis of 732 patients with an elevated platelet count. Journal of internal medicine. 1999 Mar 1;245(3):295-300.Harrison CN, Bareford D, Butt N, Campbell P, Conneally E, Drummond M, Erber W, Everington T, Green AR, Hall GW, Hunt BJ. Guideline for investigation and management of adults and children presenting with a thrombocytosis. British journal of haematology. 2010 May 1;149(3):352-75.Hay D, Hill M, Littlewood T. Neutropenia in primary care. BMJ: British Medical Journal. 2014 Sep 11;349.Honda T, Uehara T, Matsumoto G, Arai S, Sugano M. Neutrophil left shift and white blood cell count as markers of bacterial infection. Clinica Chimica Acta. 2016 Jun 1;457:46-53.Insiripong S, Supattarobol T, Jetsrisuparb A. Comparison of hematocrit/hemoglobin ratios in subjects with alpha-thalassemia, with subjects having chronic kidney disease and normal subjects. Southeast Asian J Trop Med Public Health. 2013 Jul 1;44:707-11.Keohane C, McMullin MF, Harrison C. The diagnosis and management of erythrocytosis. BMJ. 2013 Nov 18;347:f6667.Kovalszki A, Weller PF. Eosinophilia. Primary Care: Clinics in Office Practice. 2016 Dec 1;43(4):607-17.Lawrie D, Coetzee LM, Becker P, et al. Local reference ranges for full blood count and CD4 lymphocyte count testing. South African medical journal. 2009 Apr; 99(4): p. 243.
Madu AJ, Ughasoro MD. Anaemia of chronic disease: an in-depth review. Medical Principles and Practice. 2017;26(1):1-9.McMullin MF. Diagnosis and management of congenital and idiopathic erythrocytosis. Therapeutic advances in hematology. 2012 Dec;3(6):391-8.
Nienhuis AW, Nathan DG. Pathophysiology and clinical manifestations of the β-thalassemias. Cold Spring Harbor perspectives in medicine. 2012 Dec 1;2(12):a011726.Pearson TC. Apparent polycythaemia. Blood reviews. 1991 Dec 1;5(4):205-13.
Perry M. Understanding blood results: the full blood count. Practice Nurse. 2012 Oct; 42(2): 12-17.Rose SR, Petersen NJ, Gardner TJ, Hamill RJ, Trautner BW. Etiology of thrombocytosis in a general medicine population: analysis of 801 cases with emphasis on infectious causes. Journal of clinical medicine research. 2012 Dec;4(6):415.Rothenberg ME. Eosinophilia. New England Journal of Medicine. 1998 May 28;338(22):1592-600.Roufosse F, Weller PF. Practical approach to the patient with hypereosinophilia. Journal of Allergy and Clinical Immunology. 2010 Jul 31;126(1):39-44.Schwartzberg LS. Neutropenia: etiology and pathogenesis. Clinical cornerstone. 2006 Jan 1;8:S5-11.Sharma S, Rose H. Incidentally detected thrombocytopenia in adults. Australian family physician. 2014 Oct 1;43(10):700.Siracusa MC, Kim BS, Spergel JM, Artis D. Basophils and allergic inflammation. Journal of Allergy and Clinical Immunology. 2013 Oct 31;132(4):789-801.Stemmelin GR, Doti CA, Shanley CM, Ceresetto JM, Rabinovich OM, Reparaz MA, Vukovic MG, Bullorsky EO. Smoking as a Cause for Mild Chronic Neutrophilia.