FBC interpretation

Question 1

Constituents of red cell count

Answer 1

Hb: concentration of haemoglobin within the blood. Hb is the protein in red blood cells which carries oxygen.

MCV: mean volume of the red blood cells

Reticulocyte count: proportion of red blood cells that are immature. Increased in blood loss and haemolytic anaemias because the bone marrow works harder to replace the lost cells.

Question 2

Other relevant if anaemic

Answer 2

WCC and platelet count: if both are also abnormal then a bone marrow cause is likely

Question 3

Microcytic (TAILS)

Answer 3

Thalassaemia 
Anaemia of chronic disease 
Iron deficiency (most common)
Lead poisoning 
Sideroblastic anaemia

Question 4

Tests for specific causes

Answer 4

Haematinics: B12, folate and ferritin
Iron studies - ferritin, iron, transferrin, total iron binding capacity, transferrin saturation, soluble transferrin receptor
TFTs
Bilirubin (unconjugated is raised in haemolysis)
Blood film +- bone marrow biopsy
Hb electrophoresis (if haemoglobinopathy expected)

Question 5

Polycythaemia

Answer 5

Increased percentage of red blood cells within the blood

Reactive polycythaemia (i.e. decreased plasma volume) - acute dehydration, chronic (obesity, HTN, alcohol excess, smoking)
Absolute polycythaemia (i.e. increased red blood cells)
Primary = polycythaemia rubra vera
Secondary = due to increased EPO bc of chronic hypoxia (e.g. COPD, altitude, congenital cyanotic heart disease) or EPO secreting tumours (RCC)

Question 6

Polycythaemia investigations

Answer 6

WCC and platelets - both raised in primary absolute but not secondary absolute
EPO level
JAK-2 mutation testing and consider bone marrow biopsy

Question 7

White blood cells

Answer 7

Lymphocyte count
Neutrophil count
Monocyte count
Eosinophil count
Basophil count

Question 8

Thromocytopaenia

Answer 8

Decreased production: bone marrow infiltration, aplastic anaemia
Increased destruction / consumption: DIC, TTP, HUS, heparin induced, ITP, SLE, CLL etc

Invesigations: blood film and bone marrow biopsy, infection screen, LFTs, LDH, B12 and folate, coag screen, acute phase proteins

Question 9

Thrombocytopaenia tx

Answer 9

ITP: observation or corticosteroids / IVIg / platelet concentration transfusion (if bleeding)
TTP: plasmapheresis + corticosteroids + FFP / rituximab
HUS: supportive / dialysis / plasmapheresis
HIT: stop heparin and give non heparin anticoagulant

Give platelets if < 10 or < 50 and bleeding (not for TTP / HUS / HIT)
Splenectomy may be considered

Question 10

Thrombocytosis

Answer 10

Primary: essential thrombocythaemia, other myeloproliferative disorders
Secondary: bleeding, infection, inflammation, malignancy

Possible investigations: blood film and bone marrow biopsy, acute phase proteins, JAK2 mutation, ferritin

Aspirin (to prevent thromboembolic disease). Hydroxycarbamide (if primary cause)

Question 11

Pancytopaenia

Answer 11

Causes: bone marrow infiltration (acute leukaemia, myeloma, lymphoma etc), myelosuppression (chemo, lead, infection), impaired haematopoesis (B12 / folate deficiency, aplastic anaemia), peripheral destruction of blood cells (autoimmune, hypersplenism)

Blood film and bone biopsy, LDH, B12 and folate, reticulocytes, electrophoresis and immunoglobulin (myeloma), viral serology, autoimmune profile etc