Why pain is so hard to measure?

When therapists ask the client how much pain they are in, it is not an opportunity for bravado, but simply an element of finding out how the condition, discomfort or pain is impacting on the clients daily life and secondly, a way of measuring changes from week to week.

When investigating pain, the basic procedure for clinics everywhere is to give a patient the McGill Pain Questionnaire. This was developed in the 1970s by two scientists, Dr Ronald Melzack and Dr Warren Torgerson, both of McGill University in Montreal, and is still the main tool for measuring pain in clinics worldwide.

Melzack began to list the words patients used to describe their pain and classified them into three categories: sensory (which included heat, pressure, “throbbing” or “pounding” sensations), affective (which related to emotional effects, such as “tiring”, “sickening”, “gruelling” or “frightful”) and lastly evaluative (evocative of an experience – from “annoying” and “troublesome” to “horrible”, “unbearable” and “excruciating”). All the words share an unfortunate quality of sounding like a duchess complaining about a ball that didn’t meet her standards.

A more recent variant is the National Initiative on Pain Control’s Pain Quality Assessment Scale (PQAS), in which patients are asked to indicate, on a scale of 1 to 10, how “intense” – or “sharp”, “hot”, “dull”, “cold”, “sensitive”, “tender”, “itchy”, etc – their pain has been over the past week.

Women who have experienced childbirth may, after that experience, rate everything else as a mild 3 or 4

The trouble with this approach is the imprecision of that scale of 1 to 10, where a 10 would be “the most intense pain sensation imaginable”. How does a patient imagine the worst pain ever and give their own pain a number? Middle-class British men who have never been in a war zone may find it hard to imagine anything more agonising than toothache or a tennis injury. Women who have experienced childbirth may, after that experience, rate everything else as a mild 3 or 4.

Pain can be either acute or chronic. Acute pain means a temporary or one-off feeling of discomfort, which is usually treated with drugs while chronic pain persists over time and has to be lived with as a malevolent everyday companion. But because patients build up a resistance to drugs, other forms of treatment must be found for it.

“I’d say that 55 to 60 per cent of our patients suffer from lower back pain,” says Adnan Al-Kaisy, who heads the Pain Management and Neuromodulation Centre at Guy’s and St Thomas’ Hospital in London, Europe’s biggest pain centre. “The reason is, simply, that we don’t pay attention to the demands life makes on us, the way we sit, stand, walk and so on. We sit for hours in front of a computer, with the body putting heavy pressure on small joints in the back.”