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Human Diseases > W17 63 essential blood tests for dentists > Flashcards

W17 63 essential blood tests for dentists Flashcards

1
Q

What are common blood tests?

A

Full blood count (FBC)
Renal function tests / urea and electrolytes (U&E)
Liver function tests LFT
CRP and ESR - to know infections and inflammations
Coagulation and INR
Virology screening eg HIV, hepatitis

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2
Q

What are the main components of a FBC?

A

Red blood cells
White blood count
Platelet count

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3
Q

What are the different parts of a red blood cell count?

A

Haemoglobin (Hb) (first value you should look at)
Mean corpuscular volume (MCV)/mean cell volume
Red cell count (RCC)
Haematocrit (HCT)/packed cell volume (PCV)
Mean corpuscular haemoglobin (MCH)/haemoglobin concentration (MCHC)
Red blood cell distribution width (RDW)

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4
Q

What does haemoglobin levels show?

A

Concentration of haemoglobin within the blood. Carries oxygen.
If low, this is anaemia.

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5
Q

What is mean corpuscular volume (MCV) / mean cell volume?

A

Mean volume of the red blood cells
Macrocytic = large cells; normocytic = normal cells; microcytic = small cells

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6
Q

What is the red cell count (RCC)?

A

Concentration of red blood cells within the blood

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7
Q

What can different red cell counts show?

A

When it increases, can be due to reduced plasma volume such as dehydration, or increased red cell production like polythasaemia
Might be decreased due to increased plasma volume such as in pregnancy, or reduced red cell production such as in bone marrow failure or bleeding.

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8
Q

What is haematocrit (HCT)/packed cell volume (PCV)?

A

Percentage of total volume of blood accounted for by RBCs
Based on volume, so also affected by mean cell volume

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9
Q

What is mean corpuscular haemoglobin (MCH)/haemoglobin concentration (MCHC)?

A

The mean quantity/concentration of haemoglobin within the red blood cells
Affects the colour of the cells: Hypochromic = pale, normochromic = normal red

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10
Q

What does red blood cell distribution width (RDW) show?

A

Measures the variation of RBC volumes
Used together with MCB to determine whether the anaemia is because of mixed cause or a single cause

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11
Q

What is anaemia?

A

Low haemoglobin

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12
Q

What tests can be used to diagnose/classify anaemia?

A

WBC and platelet count
Reticulocyte count
Mean corpuscular volume (MCV)

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13
Q

What is the likely cause of anaemia if WBC and platelet counts are abnormal?

A

Bone marrow cause

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14
Q

What is the likely cause of anaemia if reticulocyte count is raised?

A

Usually due to blood loss or haemolytic anaemia such as sickle cell disease and thalassaemia

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15
Q

What is the likely cause of anaemia if MCV is reduced?

A

Likely thalassaemia

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16
Q

What are some causes of anaemia by MCV? (TABLE PG621)

A

Microcytic - thalassaemia, iron deficiency
Normocytic - acute blood loss, haemolytic anaemia, chronic kidney disease (decreased erythropoietin)
Macrocytic - megaloblastic: decreased B12 or folate, drug induced; non-megaloblastic: alcohol, reticulocytosis, liver disease

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17
Q

What other further investigations can be done for anaemia?

A

Haematinics: B12, folate, ferritin
Iron studies
TFTs - thyroid function tests
Bilirubin
Blood film +/- bone marrow biopsy
Hb electrophoresis - for haemoglobinopathy such as sickle cell diseases

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18
Q

Why are TFTs useful for anaemia?

A

Low thyroid levels will have normocytic or microcytic anaemia with increased MCV

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19
Q

Why is testing bilirubin useful in anaemia?

A

Unconjugated bilirubin is raised in haemolysis. So patients with haemolytic anaemia will have raised haemoglobin levels.

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20
Q

What are the commonest causes of anaemia?

A

Iron deficiency anaemia
B12-deficiency anaemia
Folate deficiency anaemia
Anaemia of chronic use
Haemolytic anaemia

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21
Q

What can iron deficiency anaemia be caused by?

A

Chronic blood loss - usually due to GIT loss, such as malignancy, inflammation, ulcers, viruses
Increased demand - during pregnancy and child growth
Decreased absorption - eg in coeliac disease, gastrectomy or other surgeries
Poor intake of iron - eg diet

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22
Q

What is the cause of B12-deficiency anaemia and what is the treatment?

A

Caused by pernicious anaemia, atrophic gastritis, malabsorption
Treatment = b12 injection every 3 months or tablets

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23
Q

What are the causes of folate-deficiency anaemia?

A

Dietary - eg alcoholism and poor diet
Increased requirements during pregnancy
Malabsorption during coeliac disease and pericreatic insufficiency
Crohn’s disease
Drugs that interfere with B12 metabolism: phenytoin, methatrexate, tremethaline - UTI drugs, will need long term folate treatment

24
Q

How do you treat folate-deficiency anaemia?

A

Folate supplements

25
Q

What dental problems can anaemia cause?

A

Increased risk for periodontitis
Pale tissue
Oral ulcerations - recurrent aphthous
Glossitis (left)

26
Q

What different white cell counts are there?

A

Neutrophils - related to bacterial infection
Lymphocytes - related to viral infection
Monocytes - related to TB, malaria, infective endocarditis
Eosinophils
Basophils

27
Q

What is the reference range for WBCs?

A

3.6-11.0 x 10^9/L

28
Q

What could be indicated if a patient presented with a dental infection and raised WBC and neutrophils?

A

Patients with dental infection with raised WBC and neutrophils is an indication that antibiotics would help with infection

29
Q

What is a high and low platelet (Plt) count?

A

High Plt = thrombocytosis - pt at higher risk of clotting
Low Plt = thrombocytopenia - higher risk of bleeding!!

30
Q

What is CRP?

A

C-reactive protein is a protein made by the liver
Marker of inflammation (not infection!)

31
Q

When do CRP levels rise?

A

Rises within hours of onset of an infection or inflammatory condition and returns to normal within 3-7 days if the acute process is resolved.

32
Q

Why is it important to know that CRP is a measure of inflammation and not infection?

A

Because if a pt complains of swelling, they might have CRP elevated which means the swelling is just due to inflammation and not infection.

33
Q

What is ESR?

A

An erythrocyte sedimentation rate (ESR) test measures how far red blood cells settle to the bottle of a test tube in 1 hour.

34
Q

How does ESR differ and what do results mean?

A

Inflammation and infection can lead to more proteins in the blood which can make them settle further in the test tube.
Increases in a slower manner and remains elevated for a longer period of time.

35
Q

What blood test results would be abnormal in giant cell arteritis?

A

High ESR
High CRP
Thrombocytosis
(patients usually present with headache and sensation of the temporal region).

36
Q

What renal function tests are there?

A

Serum sodium
Serum potassium
Serum urea
Serum creatinine
Estimated glomerular filtration rate (eGFR)
(urea and electrolytes tests)

37
Q

How are U&E’s a measure of renal/kidney function?

A

The kidney excretes urea and creatinine, so high levels indicate reduced renal function.
Sodium and potassium are included in the panel as renal dysfunction can lead to electrolyte derangements

38
Q

What non-renal, medication related causes might cause electrolyte balance?

A

Commonly ACE inhibitors, duratics, anticoagulants, carbamazapine, lithium, digoxin
- ACE inhibitors and duratics are commonly used in treating high BP
- Duratics also in fluid retention
- Carbamazepine used to treat neuropathic pain
- Lithium for bipolar disorder
- Digoxin for heart arrhythmias or fast AF

39
Q

What can high urea levels indicate (non-renal cause)?

A

Can indicate upper gastrointestinal haemorrhage. In upper GI bleeds urea is raised because of haemoglobin breakdown, important marker.

40
Q

What medications can affect impaired renal function (dentist relevant prescribing)?

A

Amoxicillin for dental infection: reduce dose if eGFR < 30, in reduced renal function so it doesn’t cause toxicity
Avoid ibuprofen in severe renal impairment - risk of fluid retention, further renal impairment including renal failure

41
Q

Why are liver function tests (LFT) taken?

A

For suspected liver disease
To monitor liver function
Monitor the effects of potentially hepatotoxic medications eg paracetamol

42
Q

What are the components of LFTs?

A

Alanine transaminase (ALT)
Aspartame aminotransferase (AST)
Alkaline phosphatase (ALP)
Gamma-glutamyltransferase (GGT)
Bilirubin
Albumin

43
Q

What are ALT and AST and what to raised levels indicate?

A

ALT and AST are enzymes found in the liver
Raised ALT/AST levels = liver cell damage

44
Q

What are some causes of raised ALT/AST levels?

A

Hepatitis (viral, alcoholic, ischaemic)
Liver cirrhosis
Drug/toxin-induced liver injury (eg paracetamol overdose)
Malignancy (hepatocellular carcinoma)

45
Q

What do raised ALP levels mean?

A

Raised ALP levels = gallbladder disease (cholestasis) or bone disease

46
Q

What do different levels of ALP and GGT mean?

A

Raised ALP but normal GGT = suggests bone disease, vitamin D deficiency, bone metastases
Raised ALP and raised GGT = more likely suggesting cholestasis
Isolated raised GGT is associated with alcohol excess

47
Q

What is bilirubin?

A

A waste product of haemoglobin breakdown.
When RBCs breakdown, it forms unconjugated bilirubin (insoluble), which binds to albumin to flow to the liver. Hepatocytes then convert it into conjugated bilirubin (soluble), and excretes this into bile. Bile gets further metabolised and excreted through stool and urine.

48
Q

What does high bilirubin indicate?

A

Jaundice

49
Q

What are the causes of jaundice?

A

Pre-hepatic: haemolysis (excessive RBC breakdown)
Hepatocellular: hepatitis, cirrhosis, malignancy, drug or toxin insult
Cholestatic (obstructive) jaundice: intrahepatic or extrahepatic (eg gallstones)

50
Q

What are some tests done for coagulation screening?

A

INR - prothrombin time (PT)
APTT

51
Q

What is INR a measure of?

A

The extrinsic pathway
Measure of overall clotting
Affected in anticoagulant use - eg warfarin or liver failure

52
Q

What is APTT?

A

Intrinsic pathway
Measures factors VIII (and VWF), IX, and XI

53
Q

What are the most common causes of increased APTT?

A

Haemophilia A (VIII), B (IX) and C (XI)
von Willebrands disease (since vWF pairs with VIII)

54
Q

What complementary tests go alongside coagulation screening tests?

A

FBC and LFTs

55
Q

When are virology screens done?

A

As part of sharp injury/body fluid exposure protocol
Includes hepatitis, HIV, CVM, EBV
Patient and operator blood needs testing

56
Q

When do you need to take a blood gas?

A

If you are going to be a DFT in oral and maxillofacial surgery

57
Q

What is part of a blood gas?

A

Arterial or venous - tells you whether pt is oxygenated properly, eg respiratory failure tests
Lactase - sepsis?
Chest oxygenation and retention

Human Diseases (75 decks)

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