Using tests to help with diagnosis

Preparation for Clinical Skills 1

Tests that you might hear discussed during clinical skills 1

• 3 patients • Each one illustrates how a clinician can use tests

to help them manage a patient• Some simple questions• Use the information we have already covered• Think about what is going on• Think about how can the test help you as a

doctor to manage a patient • Discussed in greater detail during CS1

From patient to diagnosis

• 44% Referring GP diagnosis unchanged• 41% Diagnosis changed after history• 7% Diagnosis changed after

examination• 8% Diagnosis changed after

investigation

Cost of Tests

• Chest X-ray £16.00

• CT chest £56.00

• Full blood count £5.00

Cost to the patient      Equivalent Dose (Sv)

Dose required to sterilise medical products     25 000

Typical total radiotherapy dose to cancer tumour     60

50% survival probability, whole body dose     4

Legal worker dose limit (whole body)     0.02

Average annual dose from all sources in Cornwall     0.008

Average annual dose from natural radiation     0.002

Typical chest X-ray dose     0.00002

Average dose from a flight from UK to Spain     0.00001

Ct scan to abdomen or pelvis delivers about 500 x radiation as a single CXR

Blood tests

Why do we do them?

1. Screen asymptomatic patients for a disease2. To confirm or refute a diagnosis3. As marker of disease progression / response

to therapy

What do you get?

Blood tests

• Blood count• Us and Es• Glucose• HbA1c• Liver function• Cholesterol• Subtypes of cholesterolSpecial blood tests• PSA• Hormones• Thyroid • Virus screens• Cultures for infection

Simple blood tests Also available to GPs

RadiologyECG24 hour ECGEchocardiogram

Full blood count

Blood count• Hb • Red cell size• White blood cells• Different types of white

blood cells• Platelets

• counts the number of red cells, white cells, and platelets per ml of blood.

• measures the size of the red blood cells and calculates their average (mean) size.

• calculates the proportion of blood made up from red blood cells (the haematocrit).

• measures the amount of haemoglobin in the red blood cells.

• http://www.patient.co.uk/health/Blood-Test-Blood-Count-and-Smear.htm

Erythrocyte sedimentation rate (ESR)

• Indirect measure of acute phase response• Measures rate of fall of erythrocytes through plasma• Depends on how red cells aggregate• May be disparity between ESR and CRP in certain

conditions

Blood biochemistry

• Urea• Creatinine

• eGFR• Sodium• Pottasium

• Glucose

• Protein waste• Muscle breakdown

indicates kidney function• Estimated Glomerular

filtration• Blood electrolytes vital for

life and cardiac function• Transportable energy

Factors affecting urea and creatinine

C-reactive protein (CRP)

• Acute phase protein• Increases within 6 hours inflammatory

stimulus• Half life 19 hours

Some examples

A patient coming for a check up

• Mr Smith • Aged 55 • Visits his GP for

routine check up • What can the GP

offer• Why does he do

this?

Cholesterol

• The total circulating cholesterol

• Low density ( bad)• High density

(“good”)• Circulating fats

• Total cholesterol – made up of:

• LDL• HDL• Triglycerides

Other tests

• Liver function

• HbA1c• PSA• Thyroid function• Hormones

• Tests liver function and when it is not working

• Glycosylated Hb – • Released from prostate• Thyroid hormones• Test endocrine function

Prevention

• What is Primary prevention and what is secondary prevention?

• Can you suggest any examples?

Reducing risk factors

• What are the risk factors for people with vascular disease?

• How can these be changed and what will the effect be?

• How does a doctor decide what to do and how does this get explained to a patient?

Mr White – Aged 62 with a history of chest tightness and shortness of

breath

• Which symptoms suggest that a patient has Angina?

• What is happening in an anginal attack?• What can be done to prevent it ?• How do we investigate it?

Initial tests

• Blood tests

• X ray of chest

• Plain ECG

Chest x ray

• Aortic knuckle

• Left ventricle

• Pulmonary arteries

• Diaphragm• Air in stomach

Resting ECG

Uses of ECG

• Looking at rhythm of the heart

• Information about conduction of electrical impulse

• Information about damage to heart muscle

• Specific patterns of appearance used to help find out about heart, electrolyte changes

Hyperkalaemia

The patient is referred to the cardiac clinic

• What can a hospital doctor do?• Exercise ECG• 24 hour ECG for heart rythm• Isotope scans looking at perfusion of heart

muscle• Angiogram to look at blood flow• Echocardiogram

Exercise ECG – Stress test

24 hour ECG

Isotope scans

Angiography

Therapeutic intervention

Balloon angioplasty Coronary stent

Echocardiogram

Mr Green 63 SUDDEN ACUTE CHEST PAIN

• Which factors on a history suggest that the pain is coming from his heart?

• What is the cause of the pain and what is the process called?

• What are the risks to the patient without prompt treatment?

• What actions can the GP or paramedic at the scene do to reduce the extent of heart muscle damage?

Cardiac chest pain?

Acute coronary syndrome ( ACS)

Pathology in a heart attack

The patient is seen in the emergency department

• What tests will help to confirm the diagnosis of a heart attack?

• What actions are used to limit the damage to the patients heart

• How are tests used to monitor the patient after the initial event?

Blood tests

• Troponins – proteins released by damaged muscle into the blood stream

• Levels elevated after 12 hours • May remain elevated for up to 2 weeks

Chemical markers in Acute coronary syndromes

Blood markers• Troponins – breakdown

products of cardiac muscle cells – suggest cellular damage

• Enzymes – some specific for Cardiac muscle

• CK MB fraction• Some non specific

ECG in MI

• There are characteristic changes • ECG can record these• Site of changes suggests location of the damage• The shape of the changes may suggest severity of the damage

Complications of MI.......

• Changes to heart rhythm – slow, fast, very fast.......

• Loss of pump function• Leaking of valves• Blood clots• Drop in blood pressure• Failure of heart pump

ECG monitoring.......

A medical emergency

Thrombolysis and primary angioplasty