Definition CBC is a blood test used to measure and evaluate cells that circulate in the blood. The test includes an actual counting of red and WBC as well as an analysis of cells viewed on a blood smear. A CBC may be useful as a screening test for underlying infection, anemia and illness.

Sample CBC WBC 4.5 to 11.0 x10^9/L RBC 4.7 - 6.1 x 10^12/L HGB 13.8 to 17.2 gm/Dl (M) 12.1 to 15.1 gm/Dl (F) HCT 40.7% to 50.3% (M) 36.1% to 44.3% (F) MCV 80 to 95 femtoliter MCH 27 to 31 pg/cel MCHC 32 to 36 gm/dL PLT 150,000 to 450,000/dL

Differential Segs......... 48%..............(51-72%) Lymphs..... 40%..............(8-35%) Monos........ 6%..............(1-9%) Eos............ 4%...............(0-9%) Baso.......... 2%...............(0-2%

Constituents of CBC – White Cells Neutrophils: Indicate bacterial infection. May also be raised in acute viral infections. Lymphocytes: Higher with some viral infections such as glandular fever. Raised in chronic lymphocytic leukemia (CLL). Can be decreased by HIV infection. Monocytes: May be raised in bacterial infection, tuberculosis, malaria, leukemia, Eosinophils: Increased in parasitic infections, asthma, or allergic reaction. Basophils: May be increased in bone marrow related conditions such as leukemia or lymphoma

Normal RBC Normal, mature RBCs are biconcave, disc-shaped, anuclear cells.

Red Cells Total red blood cells: The number of red cells is given as an absolute number per litre. Iron deficiency anemia shows up as a Low RBC count. Hemoglobin: The amount of hemoglobin in the blood. A low level of hemoglobin is a sign of anemia. Hematocrit or packed cell volume (PCV): This is the fraction of whole blood volume that consists of red blood cells. MCV: the average volume of the red cells. Anemia is classified as microcytic/macrocytic or normocytic. Other conditions that can affect MCV include thalassemia, reticulocytosis, alcoholism, chemotherapy, B12 deficiency, and/or folic acid deficiency.

MCH: the average amount of hemoglobin per red blood cell. MCHC: the average concentration of hemoglobin in the cells. RDW: the variation in cellular volume of the RBC population. Platelets: numbers are given, as well as information about their size and the range of sizes in the blood. MPV: a measurement of the average size of platelets.

Other relevant tests Other relevant tests WCC and platelet count: if both also abnormal, a bone marrow cause is likely Reticulocyte count: if raised, the cause is blood loss or haemolytic anaemia Mean cell volume (MCV): Anaemia = “a reduced concentration of haemoglobin within the blood” Anaemia

Anaemia= A reduced concentration of haemoglobin within the blood.

Tests for specific causes Haematinics: B12 & folate, ferritin (NB. ferritin is also an acute phase protein) Iron studies: iron, transferrin/ total iron binding capacity (TIBC), transferrin saturation, ferritin, soluble transferrin receptor TFTs Blood film ± bone marrow biopsy (if bone marrow cause/haemolytic anaemia/sideroblastic anaemia suspected) Hb electrophoresis (if thalassaemia/ sickle cell suspected) Bilirubin (raised in haemolysis)

Commonest Causes of Anamia Iron-deficiency anaemia o Physiology: iron is found in red meats (haem iron) and cereal (non-haem iron). In humans, 2/3 is stored as haem, 2/9 as ferritin, 1/9 as haemosiderin. Fe2+ (ferrous) is absorbed; Fe3+ (ferric) is consumed and used. o Causes: Chronic blood loss (1. Menstrual loss; 2. GI tract loss e.g. malignancy, ulcers, varices; 3. Urinary tract loss) ↑demand (pregnancy, growth)upper GI bleeding) ↓absorption (coeliacs, gastrectomy) Poor intake o Investigations if no clear cause: upper GI endoscopy + colonoscopy, coeliacs screen, urine dipstick o Treatment: treat cause, ferrous sulphate tablets, transfusion if Hb<70

B12-deficiency anaemia o Physiology: vitamin B12 is found in meat and dairy products. The stomach produces intrinsic factor which binds to B12, allowing it to be absorbed in the terminal ileum. Body stores last up to 4 years. Causes: pernicious anaemia, malabsorption (e.g. after gastrectomy or terminal ileum disease/resection Investigations for pernicious anaemia: parietal cell antibodies, intrinsic factor antibodies, Schilling’s test Treatment: treat the cause, hydroxocobalamin (B12) injections 3-monthly

Folate-deficiency anaemia o Physiology: folate is found in green vegetables. Body stores only last 4 months (therefore deficiency develops earlier in malabsorption/pregnancy). o Causes: Dietary (alcoholism, neglect) ↑requirements (pregnancy, haematopoiesis) Malabsorption (coeliacs, pancreatic insufficiency, gastrectomy, crohns) Drugs interfere with metabolism (phenytoin, methotrexate, trimethoprim) o Treatment: treat cause, oral folic acid supplements

Anemia of chronic disease o Causes: any chronic disease o Classically: iron ↓, TIBC ↓, ferritin normal (vs. iron deficiency anaemia: iron ↓, TIBC ↑, ferritin ↓) o Treatment: treat cause, transfuse if Hb<70

Haemolytic Anaemia o Inherited causes: Haemoglobinopathies: sickle cell, thalassaemia Membrane defects: hereditary spherocytosis, elliptocytosis Enzyme defects: G6PD deficiency, pyruvate kinase deficiency o Acquired causes: Immune mediated: autoimmune haemolytic anaemia, drug-induced haemolytic anaemia, alloimmune haemolytic anaemia Non-immune mediated: DIC, TTP, physical damage by e.g. heart valves, toxins such as lead/uraemia/drugs, malaria, paroxysmal nocturnal haemoglobinuria

Polycythaemia “increased concentration of red blood cells within the blood” Causes:- Relative polycythaemia (i.e. ↓plasma volume) o Acute dehydration o Chronic (associated with obesity, hypertension, alcohol excess, smoking)  Absolute polycythaemia (i.e. ↑RBC mass) o Primary = polycythaemia ruba vera o Secondary = due to increased EPO (e.g. RCC) or chronic hypoxia (e.g. COPD, altitude, congenital cyanotic heart disease) Causes  Polycythaemia = “increased concentration of red blood cells within the blood” Polycythaemia

Platelets Thrompocytopenia Causes: o Secondary immune: SLE, CLL, viruses, drugs, alloimmune Platelets Thrompocytopenia Causes: o Decreased production: bone marrow failure, aplastic anaemia, megaloblastic anaemia, myelosuppression Increased destruction/ consumption o Non-immune: DIC, TTP, HUS, sequestration in hypersplenism (including portal hypertension e.g. in liver disease) o Primary immune: ITP o Secondary immune: SLE, CLL, Viruses & drugs. Causes  Thrombocytopenia

Thrombocythemia Causes:- Primary: essential thrombocythaemia, other myeloproliferative disorders Secondary: bleeding, inflammation, infection, malignancy, post-splenectomy

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