Blood Tests Flashcards
FBC?
- RBC tests
- WBC tests
- Platelet tests
What RBC tests are included in the FULL BLOOD COUNT?
- Red cell count (RCC): the number of red cells present per unit volume of blood
- Haematocrit (Hct): % of the blood sample that is made up of red cells
- Mean corpuscular volume (MCV): the average size of the red cells
- Reticulocyte count: the number of reticulocytes (immature red cells)
- Haemoglobin
- Mean corpuscular haemoglobin (MCH): the amount of haemoglobin per red blood cell
- Mean corpuscular haemoglobin concentrate (MCHC): average concentration of haemoglobin in a given volume of blood
What does haematocrit mean?
% of the blood sample that is made up of red cells
What does MCH (mean corpuscular haemoglobin) mean?
the amount of haemoglobin per red blood cell
What does MCHC mean? (Mean corpuscular haemoglobin concentrate)
Average concentration of haemoglobin in a given volume of blood
What white cells tests are included in the FBC?
- Total white cell count (WCC)
- White cell differential
(eosinophils,neutrophil, lymphocyte, monocyte, basophil)
What does high haemoglobin indicate?
High haematocrit = too many rbcs = abnormally high haemoglobin concentration
= polycythaemia
———————————————-
- Absolute polycythaemia - increase in the number of red cells
- Relative polycythaemia - decrease in the amount of blood plasma (the liquid component of blood)
Cause of primary polycythaemia?
Caused by an issue in the bone marrow leading to a proliferation of red cell precursors
myeloproliferative neoplasms (e.g. polycythaemia rubra vera)
Causes of secondary polycythaemia?
Either cause a chronic state of hypoxia OR ectopic EPO production.
Smoking
Excess alcohol intake (can also cause low blood cell counts)
COPD
Obstructive sleep apnoea
Cyanotic heart disease
Lung fibrosis
Exogenous steroids
Certain malignancies (renal cell carcinoma, cerebellar haemangioma, Wilm’s tumour)
EPO abuse (e.g. in athletics)
Endogenous steroids (Conn’s syndrome, Cushing’s syndrome)
What is a high WCC called?
Leukocytosis
Common causes of acute leukocytosis
Reactive: infection, inflammation, post-surgery
Steroids: stress response (i.e. endogenous steroids) or medication (i.e. exogenous steroids)
Haematological: acute leukaemias
Common causes of chronic leukocytosis
Reactive: chronic infection, smoking
Haematological: leukaemia, certain subtypes of lymphoma
Hyposplenism: typically mild
Pregnancy
What is a low WCC called?
Leukopenia
Common causes of leukopenia?
Infection: can be seen as a transient phenomenon in viral illness or as a result of consumption in sepsis
Medications: antibiotics, immunosuppressants, anti-epileptics, cytotoxic agents (e.g. chemotherapy)
B12/folate deficiency
Autoimmune disease
Iron deficiency
HIV
Racial variation: middle eastern and black patients can have lower baseline neutrophil counts which are not pathological
Bone marrow failure: often this will be seen alongside low platelets and low haemoglobin
What is a low platelet count called?
Thrombocytopenia
What is a high platelet called?
Thrombocytosis
Causes of acute thrombocytopenia?
Consumption (e.g. infection, bleeding)
Acute viral infection
Medications (e.g. antibiotics, anti-epileptics, cytotoxic agents)
Disseminated intravascular coagulation/microangiopathic haemolytic anaemia (e.g. TTP, HUS)
Heparin-induced thrombocytopenia (HIT)
Immune thrombocytopenic purpura (ITP)
Pregnancy: pre-eclampsia/HELLP syndrome
Causes of chronic thrombocytopenia?
Hypersplenism
Cirrhosis
Alcohol excess
Medications (e.g. anti-epileptics, cytotoxic agents)
ITP
Autoimmune disease
B12/folate deficiency
Iron deficiency
HIV
Hepatitis B/C
Haematological disease
Bone marrow failure
Causes of thrombocytosis?
Reactive: inflammation/infection
Myeloproliferative disorders: typically essential thrombocythaemia although any myeloproliferative disorder can elevate platelet counts
Iron deficiency
Hypospenlism/post-splenectomy
Underlying malignancy: likely secondary to underlying inflammatory processes
What do U&Es include?
Estimated glomerular filtration rate (eGFR)
Serum creatinine
Serum urea
Serum sodium
Serum potassium
Reasons for ordering U&Es?
- To assess RENAL FUNCTION.
The kidney excretes urea and creatinine => markers of renal function.
Sodium and potassium are included in the panel, as renal dysfunction can lead to electrolyte derangements. - Suspected electrolyte disturbances due to non-renal causes
- Medication monitoring (e.g. after starting ACE inhibitors)
- Assessing urea levels in the case of suspected upper GI bleed/ haemorrhage.
Common drugs which require monitoring of U&Es include?
- ACE inhibitors
- ARBs
- DOACs
- Diuretics: spironolactone, thiazide diuretics (e.g. indapamide), loop diuretics (e.g. furosemide)
Carbamazepine
Lithium
Digoxin
Causes of raised serum urea?
- Renal dysfunction
- Dehydration (due to increased ADH = more urea and water reabsorption)
- Upper GI bleed (the blood is metabolised into urea)
Causes of hypernatraemia?
- Dehydration
- Diabetes insipidus
- Drugs (ie loop diuretics)
- Osmotic diuresis
- Extreme salt intake
Causes of hyponatraemia?
- SIADH (excess ADH = excess water)
Causes of hyperkalaemia?
Renal: decreased renal excretion (e.g. AKI or CKD)
Medications: ACE inhibitors, potassium-sparing diuretics, potassium supplements
Tissue damage: burns, rhabdomyolysis
Metabolic: diabetic ketoacidosis
Endocrine: Addison’s disease
Causes of hypokalaemia?
- GI K+ loss - due to diarrhoea
- Renal K+ loss - due to diuretics etc
What is a bone profile?
Calcium, phosphate, albumin, ALP
ALP rise with and without GGT rise?
- An ALP rise withnormal GGTsuggests increased bone turnover => Paget’s or bony metastases??
- An ALP rise withassociated GGT riseis more suggestive of cholestasis
Coagulation screen?
- PT/INR
- APTT
- Bleeding time
- Thrombin time
- EXTRA TESTS (thrombophilia screen, specific factors or antibodies etc)
What is PT
Assesses the extrinsic pathway
Measures factor VII
What is APTT?
Assesses the intrinsic pathway
=> measures factors VIII (and vWF), IX, and XI.
Most common causes of increased APTT?
Haemophilia A (VIII), B (IX), C (XI), and possibly von Willebrand’s disease
What is PT/INR?
A measure of overall clotting factor synthesis or consumption.
This test can be affected by liver disease, disseminated intravascular coagulation (DIC), vitamin K deficiency and warfarin levels.
What is thrombin time?
This is a test of how fast fibrinogen is converted to fibrin by thrombin.
Prolonged thrombin time => can be due to DIC, liver failure, malnutrition, abnormal fibrinolysis and many other conditions.
Common results in coagulation screen for haemaphilia A/B/C?
Raised APTT
(because this assesses the intrinisc pathway = factors 8, 9 and 11)
Common results in coagulation screen for DIC?
LOW platelet count
RAISED:
- PT/INR
- APTT
- Bleeding time
Common results in coagulation screen for Von Williebrand disease?
RAISED bleeding time
Normal or RAISED APTT
What is a lipid profile?
Cholesterol plasma concentrations.
- total chol.
- HDL-C
- non-HDL-C (including LDL-C)
- TOTAL CHOL to HDL ratio
Triglyceride plasma concentrations.
Reasons for requesting a lipid profile?
- Screening - QRisk3
- Recent CVS event (MI or stroke) for future risk reduction
- Monitoring for patients with hyperlipidaemia
Secondary causes of hypercholesterolaemia?
Pregnancy
Hypothyroidism
Cholestatic liver disease
Nephrotic syndrome
Drugs (e.g. diuretics, ciclosporin, corticosteroids, androgens)
Secondary causes of hypertriglyceridaemia?
Uncontrolled diabetes mellitus
Chronic kidney disease
Hepatocellular liver disease
Alcohol excess
Metabolic syndrome (including impaired glucose tolerance, hypertension, central obesity)
Drugs (e.g. beta-blockers, retinoids and corticosteroids)
What is haematinics + why???
Vitamin B12 (cobalamin), vitamin B9 (folate), and iron.
Haematinics are the nutrients needed by the bone marrow to make blood cells during hematopoiesis.
Without adequate amounts of these nutrients, cytopenia(s) and related symptoms can develop. Excess amounts can also be pathological and can point to various underlying disease states.
