Diagnosing disease

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Diagnosing disease

Diagnosis involves finding out the nature and causes of a persons ill health. An accurate diagnosis enables a health proffessional decide on the most appropriate treatment for the patient. A diagnosis should cover the full range of ill health problems affecting the patient. 

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The GP consultation

The first stage of diagnosis process take splace in a GP's surgery. 

During a consulatation the GP will take a medical history. This includes asking the patient to describe what is wrong and listening carerfully to the patients reply. The GP is likely to ask questions about the persistence, duration and intensity of symptoms. The GP uses an unstructured interview technique called the clinical interview in which questions are influenced by the replied to previous questions. 

A GP is also likely to ask about:

  • Previous illness and treatment
  • Whether or not the patient is currently recieving any other treatment or medication 
  • The patients lifestyle and occupation 
  • Previous history of disease in other family members
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The GP consultation

The features of an illness that are reported by the patient are called symptoms. Features of an illness that the observer (in this case the GP) can detetc are called signs. Signs are objective whereas symptoms might only be accesible by the patient themselves. 

At the same time the GP will observe the appearence of the patient looking for signs such as pallor (an unhealthy pale appearence), confusion, anxiety, if the person is overwight and breathing difficulties. 

The GP is also likeloy to look at the patients medical records, inorder to become familiar wiht the patients previous history (medical history) of illness and treatment. This can give important clues for diagnosis. 

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The physical examination

The Gp might then conduct a physical examination in order to detect further signs of disease. The more evidence collected, the more likely it is that the diagnosis will be correct.

A physical examination can involve:

  • visual examination 
  • use of a stethescope 
  • palpatation 
  • percussion 
  • reflex testing 
  • meauring temperature 
  • measuring blood pressure 


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Visual examination

Visual examination means looking at the affected part of the body. This can reveal condiditions such as arthiritus, which causes visible swelling and distortion to some joints as well as skin rashes. Patients may be asked to undress partly and some people find this embarrassing- this is a negative. 

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A stethescope is a simple device that channels sound from a small metal dish along two tubes to the GP's ears. No amplification is involved. By placing the stethescope against a patients body in various places, a GP is able to listen to the heart, arteries and lungs and digestive sytem. For example, heart arrythimas will sound different from normal, regular, two-noise heartbeat. 

Breathing will sound noisy if the airways are obstructed or if there is excess fluid present in the lungs. A stethescope is also used when measuring blood pressure. 

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Palpatation means feeling part of the patinets body with the fingers. This helps to detetct abnormalities in organs such as, tumours or swellings that can be felt through the skin. Ppalpatation enables the GP find out whether or not the patient feels pain when the organ is subjected to light pressure. 

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Percussion is a diagnostic technique in which a GP holds one or two fingers against the patients body then taps these fingers with the other hand while listening to the resulting sound. This is useful for assesing the condition of the lungs. A hallow sound indicates that the lung is clear of fluid however if some fluid is present the sound will be dull and muffled. 

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Reflex testing

Reflex testing enables a GP to detect damage to nerve pathways. The patellar (knee jerk) reflex is tested when the leg is relaxed and the weight of the leg is supported entirely by the thigh. The patient sometimes sits with one leg crossed over the other knee. A point just below patella (knee cap) is trapped using a rubber hammer. This stretches the tendon and sends a nerve impulse from the spinal cord. This triggers another nerve impulse from the spinal cord, which triggers the thigh muscle to contract. The result is that the lower leg jerks upwards. Absence of a relfex response might indicate damage or disease to the nerve pathway or to the spinal cor. This might aid the GP to assess whether a persons back pain caused by a muscle strain. 

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A GP might measure a patinets temperature using a thermometer placed in the mouth. Some thermometers are in the form of a closed glass tube containing mercury, which expands along the tube when heate. Others are digital electronic devices with a probe at one end which is placed under the patinets tounge. 

Alternatively, an infared ear thermometer might be use. A reading around 37 degrees is normal. Temperatures above this indicates a fever, which can occur with a number of infectious diseases, such as flu and meningitus. 

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Blood pressure

Blodd pressure measuremement is useful in assesing the condition of a patients cardiovascular system. High blood pressure (hypertension) is a fairly common condition, particularly among older people and obese individuals. It increases the risk of strokes and kidney disease. A person who is aerobically fit is likely to have low resting blood pressure. However, low blood pressure can be a sign of diabetes. 

A sphygmomanometer measures blood pressure as systolic, when the heart contracts, and distolic when it relaxes. An inflatable cuff attached to the sphygmomanometer is wrapped around the upper arm (above the elbow) and inflated then deflated while a doctor listens to the blood flow through an artery using a stethescope. 

A sustained level of high blood pressure is called hypertension and abnormally low blood pressure is termed hypotension. 

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Diagnostic tests

Sometimes the GP will conduct independent confirmation of a diagnosis. In such cases and also where the GP has been asked to provide a check of the patients genersal health, the GP will request one or more diagnostic tests. For example the GP may take a sample of blood or request for a urine sample off the patient. These samples are then sent off to a diagnostic laboratory for processing. This is likely to take several days and so the patient will be asked to return several days later. 

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Use of computers

GP's can use computers in several ways to aid diagnosis. One way is by looking at a dtatabase that includes a patients medical records, to check for previous illnesses and treatments. Another way is by using clinical decision support systems (CDSS). These systems enable GP's and other health workers to access information complied by expertsin diagnosing and treating a wide rang of diseases. 

Such support systems are intended to help with diagnosis as well as perscribing treatment. Some systems enable the GP to type in information such as data about blood pressure, test results and answers to various diagnostic question. A range of possible diagnoses and this helps the GP to consider conditions that might not otherwise have occured to them. 

Our widely used sytem is called PRODIGY which was developed in the UK. Another system is called ISABEL, which specialises in diagnosing conditions in children and young people. 

One advantage of CDSS is that it can reduce medical errors in diagnosis and treatment. A diasadvanatage is that practitioners can rely on it too much instead of improving their own knowledge and expertise.  

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Referral to a medical specialist

Where a disease is diagnosed that will require hospital treatmentr, or in cases where diagnosis is uncertain but a serious medical condition is suspected, the GP will refer the patient to a specialist medical consultanat. A consultant specialises in just one area of medicine, such as cardiology or othopaedics, whereas a GP can be consulted about any medical condition. 

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