Diagnosing disease

Diagnosing involves finding out the nature and causes of a person's ill health. 

Accurate diagnosis by a health professional will help decide the most appropriate form of treatment for the patients. 

Diagnosis should discover the full range of ill health problems affecting the patient so that it can be effective. The disease process and the agents that are causing the illness should be covered if the process is to be effective. It would be less effective if the patient was suffering from more than one disease but only one was diagnosed. There are several steps to the process:

• taking the patient's medical history
• the physical examination
• diagnostic tests 
• the use of computers
• referral to a medical specialist.

This will include a patient's own account of the illness and asking questions to clarify the situation and make a provisional diagnosis.

The GP will ask the patient to describe what is wrong and will listen carefully to their replies. The GP will ask key questions about persistance, duration and intensity of the symptoms. The GP uses an unstructures interview called the 'clinical interview'.

The GP will also ask about:

• previous illness and treatment
• if the patient is on medication or is having any other treatment
• the patient's lifestyle and occupation
• previous history of disease. 

The features of an illness reported by the patient are called symptoms. The features of an illness that the GP can detect are called signs. The GP will also observe the appearance of the patient. During the clinical interview, the GP is likely to be considering possible alternative diadnoses. The GP is also likely to look at the patient's medical records, this can give important clues for diagnosis.

The GP may 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.

Visual examination: looking at the affected part of the body, where this is possible. This can reveal conditions such as arthritis. Patients might be asked to partly undress to aid visual examination, and some people find this embarassing.

A stethoscope: a simple device that channels sound from a small metal dish along two tubes to the GP's ears. By placing the stethoscope against the patient's body in various places, a GP is able to listen to the heart, lungs and arteries. 

Palpation: feeling part of the patient's body with the fingers. This helps to detect abnormalities on organs, such a tumors that can be felt through the skin. It also allows the GP to detect pain when the organ is subjected to pressure.

Percussion: GP holds one or two fingers against the patient's body then taps these fingers with the other hand while listening to the resulting sound. 

Reflex testing: detect damage to the nerve pathways. The patella reflex is tested when the leg is relaxed and the weight of the leg is supported entirely by the thigh. A point below the patella is tapped using a rubber hammer, this stretches the tendon and sends a nerve impulse to the spinal cord. This triggers another nerve impulse from the spinal cord, which triggers the thigh muscle to contact, and the leg jerks. Absence of a jerk may indicate damage or disease to the nerve.

Measuring temperature: using a digital thermomiter in the mouth, ear, under the arm or anus. Digital electronic thermomiters are commonly used. A reading of around 37 degrees celcius is normal, above this indicates a fever. 

Measuring blood pressure is useful in assessing the condition of the patient's cardiovasular system. Hypertension is fairly common among older and obses people. Low blood pressure is not always a sign of disease. A person who is arobically fit is likely to have a low blood pressure, however, this can also be a sign of disease. 

Blood pressure is measured using a digital sphygmomamometer or some surgeries may use a traditional sphygmomamometer which uses a stethoscope. 

• A cuff is places around the patient's upper arm. 
• It is inflated which stops the blood flowing past the cuff along the artery leading to the hand.
• The machine then releases the pressure slightly - if using a stethoscope a pulse will be heard which is the sound caused by the blood being squirted through the constriction in the artery- systolic blood pressure.
• As more air is released from the cuff the sound dissapears, this means there is no pressure difference between the air in the cuff and the blood at its lowest pressure. There is no resistance from the cuff so the sound being pushed past the constriction ceases. This is diastolic pressure.
• Blood pressure is measured in millimetres so a reading will be 100/65.

The GP may be able to make a diagnosis having taken a medical history, questioned and observed the patient and carried out a physical examination. However there is a huge range of diseases that a GP cannot be expected to make a diagnosis without further help. The GP may request one or more diagnostic tests. These can be blood tests, urine test etc. These samples are sent off to diagnostic labratories for processing. This is likely to take several days and therefore the patient will need to make a further follow up appointment. Some other tests may require specialist equipment and require the patient to visit a hospital.

Gp's use computers in several ways to aid diagnosis.

A database that includes a patient's medical records, checks for previous illnesses and treatments. GP's also use clinical decision support systems (CDSS). This allows the GP to access information compiled by experts in diagnosing and treating a wide range of diseases. Such support systems are intended to help with diagnosis as well as prescribing treatments. 

Some systems enable the GP to type information such as data about blood pressure, test results and answers to various diagnostic questions. A range of possible diagnoses are suggested. One such system is called PRODIGY. Some GPs refer to text books during consultation even refer the patient to websited such as Patient net.

If a disease is diagnosed and requires hospital treatment or if a GP is uncertain about a diagnosis they may refer the patient to a specialist medical consultant. These are individuals who specialise in one area of medicine.