Lab Tests Flashcards
What 3 categories can a standard FBC be broken into?
Red cell tests, white cell tests and platelets
What does an abnormally high mumber of red cells or haemoglobin indicate?
Polycythaemia
What is anaemia?
A decrease in the total Hg in the blood
What is the haematocrit?
% of the blood made up by red cells
What are the types of polycythaemia?
- Absolute - increase in number of red cells
- Relative - decrease in amount of blood plasma due to low fluid intake or excess fluid loss (burns)
Absolute split into
- Primary - myeloproliferative neoplasms (polycaethaemia rubra Vera)
- Secondary - COPD, smoking, obstructive sleep apnoea…these all increase EPO which stimulates bone marrow to make more RBCs
What causes a microcytic anaemia?
TAILS
Thalassaemia, anaemia of chronic disease, IDA, lead poisening, sideroblastic anaemia
What causes normocytic anaemia?
Anaemia of chronic disease, acute blood loss, increased plasma, haemolysis, thalassaemia, hypersplenism, aplastic
What causes macrocytic anaemia?
B12/folate, toxins (alcohol, chemo), liver disease, reticulocytosis, pregnancy, myeloma, myelodysplastic disease, hypothyroidism
What can a raised hematocrit cause?
Hyperviscosity syndrome - thrombi, headaches, blurred vision, chest pain
What is a red cell count useful for?
Use with Hg and haematocrit for anaemia
What is the RDW?
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)
What does the reticulocyte count show?
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
What do you call a low WCC? What is important to determine following this?
Leukopenia
Type of white cell which is low and rate of fall
Causes of leukopenia?
- 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
What is a high white cell count called?
Leukocytosis
Common causes of acute leukocytosis?
- reactive: inflammation, infection, smoking
- haematological: acute leukaemia
- steroids: stress, medication
Common causes of chronic leukocytosis?
Reactive: chronic infection, smoking
Haematological: leukaemia, subtypes of lymphoma
Hyposplenism - typically mild
Pregnancy
Causes of lymphocytosis?
Viral infection Smoking Hyposplenism/post-splenectomy Malignancy: leukaemia and some lymphomas Pertussis
Causes of lymphopenia?
Infection Older age Alcohol excess HIV Autoimmune disease Bone marrow disease Medications: cytotoxic agents, immunosuppressants Renal failure Congenital immunodeficiency
What do monocytes become in the periphery? What do these do?
Macrophages and dendritic cells - phagocytosis, APCs, cytokine production
Causes of monocytosis?
Bacterial infection, autoimmune disease, steroids
Causes of monocytopenia?
Not clinically relevant unless very low Acute infection Steroids Bone marrow failure Cytotoxic agents Hairy cell leukaemia
Which cells are implicated in asthma?
Eosinophils, basophils, mast cells
What causes eosinophilia?
Allergies/atopy Parasite infection Autoimmune- vasculitis Medications - antibiotics, anti-epileptics, allopurinol GI disease - eosinophilic oesophagitis Respiratory disease Solid organ or haematological malignancy
