Measuring Pain

Self-report measures 

The main method used is a clinical interview, where the doctor and patient take part in a conversation which is used to develop a diagnosis for the pain. This mainly focuses on open-ended questions, so that the patient can develop their symptoms without being limited. 

Other methods used that can be useful for doctors to assess pain in questionnaires are:

• Box scale 

• Verbal rating scale 

• Liker-type scale

• Pain diary to monitor when the pain is happening and how the patient feels.

Strengths:

• Useful for understanding the feelings of patients.
• Subjective measure, which is valid when measuring pain since every individual will experience it differently.

Weaknesses:

• Subjective measure, which leaves questions up to the interpretation of physicians and might be affected by bias.
• May not be the most useful method to prescribe medicines because the information received is purely from the patients and there is nothing scientific to prove it. 

Psychometric measures 

One standardised psychometric measure is the McGill Pain Questionnaire (MPG), designed by Melzack (1975). The questionnaire consists of four main tasks that the patient has to complete:

1. A diagram of a body is shown to the patient, who has to mark where the pain is located on their body.
2. There are 20 sub-classes of descriptive words from which the patient can only choose one per class. This creates the pain rating index as the words further down the list score more points. Patients may leave out any category that is not suitable for their type of pain.
3. Then, the patient needs to describe their pattern of pain from three sub-classes of words. Also, they are asked to give some qualitative data on what helps relieve the pain and what increases it.
4. This asks the patients to rate how strong the pain is using six questions. It uses a Likert scale from 1 being Mild and 5 being Excruciating. The scores are added up to create a present pain intensity score.

Strengths:

• Ecological validity – the questionnaire is used vastly around the world, with translations to French, Portuguese and other languages. Since real patients are used, therefore the method is likely to be successful in other real-life settings.
• Quantitative and qualitative data – the questionnaire gathers a large amount of quantitative data, which cannot be affected by doctor’s subjectivity and is very easy to understand and organise. On the the other hand, qualitative data is useful for measuring pain because it is a very subjective feelings, therefore patients are not limited from writing other symptoms or descriptive words. Overall, the use of the two types of data combined creates a more holistic method of measurement.

Weaknesses:

• Lacks validity – the questionnaire does not fully measure what it has set out to because patients need to have a high literacy level in order to understand some of the words included. This makes the method less reliable as patients may answer without knowing the definitions of certain words, so technically they would be lying.
• Ungeneralisable to children – the method may not be suitable to measure pain in children because they are non likely to understand the words used. Also, the questionnaire may be complicated to use because it asks for specific tasks to be completed. Therefore, the McGill Pain questionnaire may not be applicable to use for children.
• Ethics – this method may cause distress to some patients who do not have high level of literacy, are not fluent in the language the questionnaire is written in or cannot read. This may make patients feel discriminated against as well as increase the chances of social desirability and demand characteristics.

Another Pain Behavioural scale that was designed by Richards et al (1982) is the UAB – Univeristy of Alabama at Birmingham. This is the process:

• Nurses need to assess the degree of pain patients are experiencing by observing their behaviour.
• The patient will be asked to perform some activities and the nurse will rate these from o to 10 depending on how much they pain is affecting the behaviour.
• The scores will be added up – the higher the score, the greater level of impairment.
• Structured clinical sessions can also be used to tailor the activities to the condition of the patient. These will be recorded and watch back by a trained observer, who will give scores.

Strengths:

• Quick measure to use as the scoring can be done in little time and easily, which leaves more time for physicians to check on other symptoms and patients.
• Easy to carry out as the patients are only asked to do certain movements or activities.

Weaknesses:

• Results may be affected by social desirability bias as the patients may not want to look as ill and in pain as they feel.
• The activities can be learned by long-stay patients and their body might get used to them, which might dissipate the pain.

Pain measures in children

Some self-report scales mentioned above are good for children, such as the visual analogue scale, box scale and verbal rating scale, as long as simple language is used for them to understand.

VARNI AND THOMPSON (1976) developed the Pediatric Pain Questionnaire, which is a simpler and easier version of the McGill Pain Questionnaire. The children need to:

1. Describe pain in their own words.
2. Choose as many adjectives as they want to in order to help describe their pain further.
3. Complete a visual analogue scale with faces.
4. Indicate where the pain is on a picture of a person.

Strengths:

• It is reliable as it has been shown to have a good test re-test rate.
• It is valid as it is tailored to children in order for their pain to be assessed without any difficulty or discrimination.

Weaknesses:

• Self-report measure, which might be affected by social desirability bias as the children may not want to upset their parents/doctors if their pain is not dissipating.
• The use open-ended questions may affect the results with subjectivity as doctors need to interpret the children’s description of their pain and the adjectives they chose.