W17 63 essential blood tests for dentists Flashcards by Sanjana Chahal

What are common blood tests?

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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What are the main components of a FBC?

Red blood cells
White blood count
Platelet count

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

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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What does haemoglobin levels show?

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

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

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

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What is the red cell count (RCC)?

Concentration of red blood cells within the blood

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What can different red cell counts show?

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

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

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

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

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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What is anaemia?

Low haemoglobin

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What tests can be used to diagnose/classify anaemia?

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

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

Bone marrow cause

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

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

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

Likely thalassaemia

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

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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What other further investigations can be done for anaemia?

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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Why are TFTs useful for anaemia?

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

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Why is testing bilirubin useful in anaemia?

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

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What are the commonest causes of anaemia?

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

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What can iron deficiency anaemia be caused by?

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

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

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What are the causes of folate-deficiency anaemia?

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

How do you treat folate-deficiency anaemia?

Folate supplements

What dental problems can anaemia cause?

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

What different white cell counts are there?

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

What is the reference range for WBCs?

3.6-11.0 x 10^9/L

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

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

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

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

What is CRP?

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

When do CRP levels rise?

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.

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

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

What is ESR?

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

How does ESR differ and what do results mean?

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.

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

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

What renal function tests are there?

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

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

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

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

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

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

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

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

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

Why are liver function tests (LFT) taken?

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

What are the components of LFTs?

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

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

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

What are some causes of raised ALT/AST levels?

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

What do raised ALP levels mean?

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

What do different levels of ALP and GGT mean?

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

What is bilirubin?

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.

What does high bilirubin indicate?

Jaundice

What are the causes of jaundice?

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

What are some tests done for coagulation screening?

INR - prothrombin time (PT) APTT

What is INR a measure of?

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

What is APTT?

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

What are the most common causes of increased APTT?

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

What complementary tests go alongside coagulation screening tests?

FBC and LFTs

When are virology screens done?

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

When do you need to take a blood gas?

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

What is part of a blood gas?

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