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Year 3 - Other Important Notes > Blood Tests > Flashcards

Blood Tests Flashcards

1
Q

List some causes of high Hb.

A
  • Dehydration
  • Diuretic therapy
  • Secondary to anoxia (high altitude, hypoxic respiratory conditions, heavy cigarette smoking)
  • Secondary cause e.g. polycythaemia rubra vera
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2
Q

Name a cause of low and high Hct.

A

Low in any anaemia and high in polycythaemia.

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3
Q

What does MCV stand for? What is MCH?

A

Mean corpuscular volume - average volume of patient’s RBCs. Helps to morphologically classify anaemia, dependent on its cause. Low = microcytic, normal = normocytic, high = macrocytic

Mean corpuscular haemoglobin - average haemoglobin content in an RBC. If low typically shows hypochromia. Can be seen in iron-deficiency and haemoglobinopathies.

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4
Q

What diagnosis does MCHC aid with?

A

Mean corpuscular haemoglobin concentration (MCHC) – average haemoglobin concentration per RBC. Helps to classify microcytic anaemias. Low levels are typical of iron deficiency or thalassaemia; very high often reflect spherocytosis or RBC agglutination.

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5
Q

What does high RDW suggest?

A

Red cell distribution width (RDW) – a measure of the variation in RBC size.

If high this suggests a large variation in sizes, seen in iron deficiency, myelodysplastic syndrome and haemoglobinopathies.

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6
Q

List some causes of thrombocytosis.

A

Reactive:

  • Blood loss
  • Infection
  • Inflammation
  • Post-splenectomy

Autonomous:

  • Genetic abnormalities
  • Malignancies
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7
Q

List some causes of thrombocytopenia.

A
  • Drugs
  • Foods
  • Infections
  • Liver disease e.g. hypersplenism
  • Alcohol
  • Nutrient deficiency
  • Pregnancy
  • Bone marrow disorder
  • Inherited
  • Bleeding - platelets initiate mechanisms that repair injury to thr vascular endothelium. Can be high (thrombocytosis) or low (thrompocytopenia)
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8
Q

What type of infections are these cells most commonly associated with?

  • Neutrophils
  • Lymphocytes
  • Monocytes
  • Eosinophils
  • Basophils
A
  • Neutrophils - bacterial
  • Lymphocytes - viral
  • Monocytes - chronic infection
  • Eosinophils - allergies/parasites
  • Basophils - viral/urticaria
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9
Q

List 3 causes of neutrophilia and neutropenia.

A

Neutrophilia

  • bacterial infection
  • steroids
  • post-surgery
  • burns
  • vasculitis
  • neoplasia

Neutropenia

  • infection
  • drugs (chemo)
  • autoimmune e.g.CTD, hereditary
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10
Q

List 3 causes of lymphocytosis and lymphopenia.

A

Lymphocytosis

  • reactive (viral infection, stress)
  • metabolic syndrome
  • primary (malignancies)

Lymphopenia

  • steroids
  • immunosuppressive agents
  • AI disease
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11
Q

List 3 causes of monocytosis.

A
  • Chronic infection (TB, syphilis)
  • IBD
  • carcinomas
  • myelodysplastic syndromes
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12
Q

List 3 causes of eosinophilia.

A
  • allergy
  • neoplastic
  • CTD
  • parasitic infection
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13
Q

List 3 causes of basophilia.

A
  • Viral infection
  • Urticaria
  • Hypothyroidism
  • Post-splenectomy
  • UC
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14
Q

What information is found through requesting U&Es?

A

Sodium, potassium, chloride, urea, creatinine

Common to also get eGFT reported

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15
Q

What are the normal ranges for sodium?

A

135-145

Hyponatraemia:

  • Na < 135; Mild:
  • 130-134, Moderate:
  • 120 -129, Severe <120

Hypernatraemia:

  • Na >145
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16
Q

Is sodium an intra/extracellular ion? How is its concentration maintined?

A

Extracellular

It is closely linked to fluid as water follows solutes by osmosis. Sodium reabsorption is increased by aldosterone in the DCT. ADH causes reabsorption of water (alone) from the collecting duct.

17
Q

How can you divide the causes of hyponatraemia? Why can it be fatal?

A

Into hypovolaemia, euvolaemia, hypervolaemia.

It can develop rapidly and water can shift into the brain causing cerebral oedema.

18
Q

Summarise the 2 causes of hyponatraemia in hypo/eu/hypervolaemia.

A

Hypovolaemia = Na lost and H2O follows

Na loss from kidneys:

  • -Addison’s Disease
  • -Diuretics
  • -Kidney Injury
  • -Osmotic diuresis

Na loss from elsewhere:

  • -Diarrhoea and vomiting
  • -Burns
  • -Fistula

Euvolaemia = Normal Na quantity, H2O gained

  • SIADH
  • Hypothyroidism
  • Glucocorticoid insufficiency
  • Water intoxication

Hypervolaemia = Excess ADH released secondary to intravascular fluid depletion (due to extravasation)

  • CCF
  • Hypoalbuminaemia e.g. cirrhosis, nephrotic syndrome
19
Q

List two causes of hypernatraemia in hypo/euvolaemia.

A

Hypovolaemia

  • Fluid loss
    • Burns
    • Diarrhoea and vomiting
  • Diabetes insipidus
  • Osmotic diuresis

Euvolaemia

  • Iatrogenic
    • Excess IV crystalloid
    • Sodium containing drugs
20
Q

What are the normal ranges of potassium? Is it mostly intra/extracellular?

What increases potassium uptake and excretion?

A

3.5- 5.0 (4.2 is normal) - levels outside this can have cardiac effects.

90% intracellular ion

  • Uptake - insulin and catecholamines
  • Excretion - aldosterone
21
Q

List 2 causes of hypokalaemia caused by:

  • increased renal excretion
  • increased cellular uptake
  • other loss
A

Increased renal excretion

  • Thiazide or loop diuretics
  • Endocrine - steroids, Cushing’s, Conns
  • RTA - hypomagnasaemia

Increased cellular uptake

  • Salbutamol
  • Insulin
  • Alkalosis

Other loss:

  • Intestinal fluid loss
  • Burns
  • Malnutrition
22
Q

What are the ranges for mild moderate and severe hyperkalaemia? What causes pseudohyperkalaemia?

A

K>5.5;

  • Mild: 5.5-5.9,
  • Moderate: 6.0-6.4,
  • Severe: >6.5 mmol/L.

Note can also be pseudohyperkalaemia due to haemolysis.

23
Q

What are the causes of hyperkalaemia caused by

  • Reduced renal excretion
  • Increased cellular release
  • Excess load
A

Reduced renal excretion

  • Acute/chronic kidney injury
  • Drugs (K sparing diuretics, ACEi, NSAIDs)
  • Addisons

Increased cellular uptake

  • Acidosis
  • Tissue breakdown e.g. rhabdomyolysis

Excess load

  • Iatrogenic
  • Massive blood transfusion
24
Q

How is urea formed in the body? List 3 causes of a low and high urea.

A

Urea is formed when ammonia is converted in the liver, and then excreted in the kidneys. It is raised in kidney injury however urea is not specific for kidney disease as there are other causes of abnormal urea.

Causes of high urea:

  • dehydration,
  • GI bleed,
  • increased protein breakdown (surgery, trauma, infection, malignancy),
  • high protein intake,
  • drugs

Causes of low urea:

  • malnutrition,
  • liver disease,
  • pregnancy
25
Q

What is creatinine a waste product of?

A

Creatinine is a waste product of the breakdown of creatine phosphate. It is excreted in the kidneys and is specific for kidney injury (but baseline depends on muscle mass).

26
Q

How is AKI defined?

A

An Acute Kidney Injury is when Creatinine rises ≥50% of baseline within 7 days or ≥26μmol/ in 48 hours (or urine output is <0.5ml/kg/hr ≥ 6 hours).

27
Q

What is ALT? What are the normal ranges?

A

Alanine Transferase (ALT) is a cytosolic enzyme, which is expressed predominantly in liver cells and is used as a marker to assess liver cell damage.

ALT < 120 IU/L: generally considered mild
ALT > 120 IU/L: generally considered severe

28
Q

List 3 common causes of raised ALT.

A

Common causes:

  • Alcohol
  • Viral hepatitis
  • Steatosis
  • MEdications toxins e.g. NSAIDs, antibiotics, statins, antiepileptics, antituberculosis drugs

Less common:

  • AI hepatitis
  • Haemochromatosis
  • Alpha-1 antitrypsin deficiency
  • Wilson’s disease

Non-hepatic causes of raised ALT (usually small)

  • Coeliac
  • Strenuous exercise
  • Muscle disease
  • Endocrine disease e.g. Hypo/hyperthyroidism
29
Q

What is AST? How can it be helpful alongside ALT? Is it better than ALT? Where is it found in the cell?

A

Aspartate Aminotransferase (AST)

Ratio of AST to ALT may provide useful information about the possible cause of liver disease: AST:ALT ratio ≥ 2.1 may be suggestive, but not diagnostic of alcohol related liver disease, while AST:ALT ratio < 2.1 may suggest hepatic steatosis or chronic viral hepatitis.

AST is expressed in the liver, as well as in the heart, skeletal muscle, kidneys, brain and red blood cells and therefore is not as liver specific as ALT. ALT is predominantly cytoplasmic and AST is present in both cytoplasm and mitochondria

30
Q

What is ALP? Where is it found?

A

Alkaline Phosphatase (ALP)

The two main sources of ALP are liver and bone, although there are also intestinal and placental isoforms. Elevations may be physiological or pathological.

31
Q

List 3 physiological and pathological causes of a raised ALP?

A

Physiological:

  • Third trimester of pregnancy
  • Adolescents, due to bone growth
  • Benign, familial

Pathological:

  • Bile duct obstruction
  • Primary biliary cirrhosis
  • Primary sclerosing cholangitis
  • Drug induced cholestasis, e.g. anabolic steroids
  • Metastatic liver disease
  • Bone disease e.g. Paget’s
  • Heart failure
32
Q

What is GGT a good marker for? What is a disadvantage?

A

Advantage/disadvantage

Gamma-Glutamyl Transferase (γGT) is a sensitive marker for hepatobiliary disease, but its use is limited by poor specificity

The use of γGT is in supporting a hepatobiliary source for other raised liver enzymes, e.g. ALP. It has limited utility as a primary liver test. If an isolated raised γGT is found, consider retesting after 3m if mildly raised (5x ULN). Consider ultrasound if γGT is >5x ULN.

33
Q

List some causes of raised GGT.

A
  • Hepatobiliary disease (often with other liver enzyme abnormalities)
  • Pancreatic disease
  • Alcoholism
  • Chronic obstructive pulmonary disease
  • Renal failure
  • Diabetes
  • Myocardial infarction
  • Drugs, e.g. carbamazepine, phenytoin and barbiturates and oral contraceptive pill
34
Q

Apart from LFTs which tell us about liver/bile duct damage, which tests can we do to assess liver function?

A
  • Haem breakdown – Bilirubin
  • Plasma proteins – Albumin
  • Clotting factors - PT/INR
  • Portal system – platelets

Year 3 - Other Important Notes (9 decks)

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