“From one to ten, how bad is it?” What a pain score can and cannot tell a doctor

In the recovery room the first question after "Can you hear me?" is almost always the same: "On a scale from zero to ten, where zero is no pain and ten is the worst pain you can imagine, how bad is it now?" I must have asked it tens of thousands of times. I have heard "seven" from a man who was reading the newspaper and "two" from a woman who was gripping the bed rail with white knuckles. This week's debate on whether we can be mistaken about our own pain sent me back to those faces, and I want to set down what I think the number is.

The scale and its promise

The numerical rating scale is simple, quick and portable. It needs no equipment and works across languages if you hold up fingers. For children we use faces, from smiling to crying, and for patients who cannot speak there are behavioural scales: grimacing, guarding, restlessness.

Behind the scale lies a principle that changed medicine for the better. In 1968 an American nurse, Margo McCaffery, proposed a definition that many of us were taught as students: pain is whatever the person experiencing it says it is, and exists whenever they say it does. Before that, pain was too often judged from the outside, by doctors who decided whether a wound "should" hurt that much. Patients from the wrong class, the wrong ethnic group, or simply the wrong temperament were believed less and treated worse. The principle of believing the patient corrected an injustice.

The International Association for the Study of Pain revised its definition in 2020 and kept the same spirit in a more careful form: pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. Its accompanying notes add that pain is always a personal experience, and that a person's report of pain should be respected.

What the number cannot do

The trouble begins when a report is treated as a measurement.

A thermometer gives you a temperature that means the same thing in Plovdiv and in Paris. A pain score does not. My "seven" and yours are not on a shared scale. They are each anchored to "the worst pain you can imagine", and imagination differs. A woman who has given birth without anaesthesia and a young man who has never been ill are not imagining the same ten.

Wittgenstein has a famous image for this in the Philosophical Investigations: everyone has a box with something in it which they call a "beetle", and nobody can look into anyone else's box. The word "beetle" can still have a use in the language, he suggests, but the thing in the box drops out of the game. I think of this every time a colleague compares two patients' scores as though they were blood pressures. The numbers have a use. What they do not do is open the box.

Context changes the report as well. During the Second World War the American anaesthetist Henry Beecher noticed that many badly wounded soldiers at the front asked for no pain relief, though civilians with comparable surgical wounds asked for a great deal. His suggestion was that the meaning of the wound mattered: for the soldier it was a way out of the battle, for the civilian a disaster. Every anaesthetist sees smaller versions. A mother after a caesarean, holding her baby, often reports less pain than her drug chart predicts. Fear raises the number; company lowers it.

And there is a danger in treating the number as a target. In the United States in the late 1990s, pain was promoted as a "fifth vital sign", to be recorded alongside pulse and blood pressure. The aim was humane. Some critics have since argued that treating the score as something to be driven down contributed to the overprescribing of opioids. A report became a quota.

So is the patient ever wrong?

Here I come back to the debate. Descartes, in the sixth of his Meditations, mentions people who feel pain in a limb that has been amputated, and uses it to show that the senses can mislead us about where a pain is. He did not doubt that the pain was felt.

My own view, from the bedside, is this. A patient can be wrong about many things connected with his pain: its cause, its location, how long it has lasted, what it means, even whether the cold swab he braced for was pain at all. What I have almost never been able to show is that a patient who sincerely says "it hurts now" is wrong about that. Not because his inner eye is perfect, but because there is no better witness for me to consult.

That gives the pain score its real status. It is not a measurement of a hidden quantity. It is testimony, given by the only witness present, in a form we have agreed to use. Testimony can be shaped by fear, by culture, by wanting to please the doctor or to be taken seriously. But a good doctor treats testimony the way a good judge does: seriously, critically, and never as if it were a meter reading.

What I would tell a young doctor

Use the number. Write it down. Compare it with the same patient's number an hour later, where it is genuinely useful, rather than with another patient's. Watch the face while you ask. And when the man reading the newspaper says "seven", do not argue with him. Ask him what seven means to him. The answer is usually more useful than the number, and it is the beginning of being believed. The card on qualia and the hard problem explains why philosophers find pain so difficult. After thirty-four years, so do I.