Lab Tests

Question 1

What 3 categories can a standard FBC be broken into?

Answer 1

Red cell tests, white cell tests and platelets

Question 2

What does an abnormally high mumber of red cells or haemoglobin indicate?

Answer 2

Polycythaemia

Question 3

What is anaemia?

Answer 3

A decrease in the total Hg in the blood

Question 4

What is the haematocrit?

Answer 4

% of the blood made up by red cells

Question 5

What are the types of polycythaemia?

Answer 5

1. Absolute - increase in number of red cells
2. Relative - decrease in amount of blood plasma due to low fluid intake or excess fluid loss (burns)

Absolute split into

1. Primary - myeloproliferative neoplasms (polycaethaemia rubra Vera)
2. Secondary - COPD, smoking, obstructive sleep apnoea…these all increase EPO which stimulates bone marrow to make more RBCs

Question 6

What causes a microcytic anaemia?

Answer 6

TAILS

Thalassaemia, anaemia of chronic disease, IDA, lead poisening, sideroblastic anaemia

Question 7

What causes normocytic anaemia?

Answer 7

Anaemia of chronic disease, acute blood loss, increased plasma, haemolysis, thalassaemia, hypersplenism, aplastic

Question 8

What causes macrocytic anaemia?

Answer 8

B12/folate, toxins (alcohol, chemo), liver disease, reticulocytosis, pregnancy, myeloma, myelodysplastic disease, hypothyroidism

Question 9

What can a raised hematocrit cause?

Answer 9

Hyperviscosity syndrome - thrombi, headaches, blurred vision, chest pain

Question 10

What is a red cell count useful for?

Answer 10

Use with Hg and haematocrit for anaemia

Question 11

What is the RDW?

Answer 11

Red cell distribution width - more in depth MCV. Shows range of largest and smallest red cell so useful for mixed anaemia (eg. Coeliac causing iron, B12 and folate deficiency). 
Shows anisocytosis (varying sizes)

Question 12

What does the reticulocyte count show?

Answer 12

Response of bone marrow to anaemia.
Raised + anaemia = red blood cells being destroyed (haemolysis or bleeding)
Low + anaemia = bone marrow problem (B12/folate deficiency, iron, aplastic anaemia, bone marrow infiltration from malignancies)
Raised + no anaemia = body compensating for haemolysis or adapting to increased oxygen demands

Question 13

What do you call a low WCC? What is important to determine following this?

Answer 13

Leukopenia

Type of white cell which is low and rate of fall

Question 14

Causes of leukopenia?

Answer 14

• infection: viral or sepsis
• meds: antibiotics, immunosuppressants, anti epileptics, chemotherapy
• B12/folate deficiency
• autoimmune disease
• iron deficiency
• HIV
• bone marrow failure
• Middle Eastern and Black often have lower baseline

Question 15

What is a high white cell count called?

Answer 15

Leukocytosis

Question 16

Common causes of acute leukocytosis?

Answer 16

• reactive: inflammation, infection, smoking
• haematological: acute leukaemia
• steroids: stress, medication

Question 17

Common causes of chronic leukocytosis?

Answer 17

Reactive: chronic infection, smoking
Haematological: leukaemia, subtypes of lymphoma
Hyposplenism - typically mild
Pregnancy

Question 18

Causes of lymphocytosis?

Answer 18

Viral infection 
Smoking 
Hyposplenism/post-splenectomy 
Malignancy: leukaemia and some lymphomas 
Pertussis

Question 19

Causes of lymphopenia?

Answer 19

Infection 
Older age 
Alcohol excess
HIV 
Autoimmune disease 
Bone marrow disease 
Medications: cytotoxic agents, immunosuppressants 
Renal failure 
Congenital immunodeficiency

Question 20

What do monocytes become in the periphery? What do these do?

Answer 20

Macrophages and dendritic cells - phagocytosis, APCs, cytokine production

Question 21

Causes of monocytosis?

Answer 21

Bacterial infection, autoimmune disease, steroids

Question 22

Causes of monocytopenia?

Answer 22

Not clinically relevant unless very low 
Acute infection 
Steroids 
Bone marrow failure 
Cytotoxic agents 
Hairy cell leukaemia

Question 23

Which cells are implicated in asthma?

Answer 23

Eosinophils, basophils, mast cells

Question 24

What causes eosinophilia?

Answer 24

Allergies/atopy 
Parasite infection 
Autoimmune- vasculitis
Medications - antibiotics, anti-epileptics, allopurinol 
GI disease - eosinophilic oesophagitis 
Respiratory disease 
Solid organ or haematological malignancy

Question 25

Role of basophils?

Answer 25

Release histamine and serotonin for immune response. Parasitic infection and allergies.

Question 26

What causes basophilia?

Answer 26

• benign if transient and not alongside neutrophilia or eosinophilia
• significantly above = myoloproliferative disorder - haematological malignancy
• allergic reactions/atopy
• iron deficiency
• chronic inflammation
• hypothyroidism
• infection

Question 27

Presence of blasts in blood differentials?

Answer 27

• acute leukaemia
• myeloproliferative disorder
• reactive = severe infection
• cytotoxic agent

Question 28

What is thrombocytopenia? What are the clinical features?

Answer 28

• reduced platelet count

- mucosal bleeding and spontaneous bruising

Question 29

Causes of acute thrombocytopenia?

Answer 29

• consumption (infection, bleeding)
• acute viral infection
• meds: antibiotics, anti-epileptics, cytotoxic agents
• DIC, haemolytic anaemia
• heparin-induced thrombocytopenia
• immune thrombocytopenia purpura
• pregnancy: pre-eclampsia/HELLP

Question 30

Causes of chronic thrombocytopenia?

Answer 30

• hypersplenism
• cirrhosis
• alcohol excess
• medications - anti-epileptics, cytotoxic agents
• ITP - immune thrombocytopenic purpura
• autoimmune
  B12/folate deficiency
  Iron deficiency
  HIV
  Hepatitis B/C
  Haematological disease
  Bone marrow failure

Question 31

Causes of thrombocytosis?

Answer 31

Reactive: inflammation/ infection 
Myeloproliferative disorders: essential thrombocythaemia
Iron deficiency 
Hyposplenism/splenectomy 
Underlying malignancy