PRISM is a novel and amazingly simple instrument that allows patients to express their feelings about their own suffering, according to two doctors writing in the August issue of the journal Psychosomatics.

PRISM, which stands for 'Pictorial Representation of Illness and Self Measure', is a kind of graphical interface in which patients are asked to express their perception of suffering in terms of its perceived 'distance' from the self. The test, being pictorial, is much quicker than a standard questionnaire, relies only minimally on language, and requires no batteries.

In the report, Stefan Büchi of the University of Zürich, Switzerland, and Tom Sensky of Imperial College School of Medicine, London, UK describe how PRISM works. The patient is shown a white metal board the size of a standard (A4) piece of paper. Fixed in the bottom right-hand corner is a yellow circle, seven centimetres across. The patient is asked to imagine that the white board represents his or her life, and that the yellow circle is his or her 'self'.

The patient is then handed a five-centimetre-diameter red disk, representing the illness, and is asked, "Where would you put the illness disk in your life at the moment?" Patients overwhelmed by pain and distress place the red disk on top of the yellow one, whereas patients who feel more in control of their pain place the disks some distance apart. Intriguingly, this measure is quantitive. In a pilot study on patients with rheumatoid arthritis, it was found that the separation between the disks is a consistent measure of perceived pain and the misery associated with it. This should make PRISM a useful research tool as well as a handy aid for the clinic.

Assessing your own internal state is hard to do accurately and honestly even when you are healthy. The last thing that distressed patients and harassed doctors and nurses need is to embark on a long, complex questionnaire, when a device such as PRISM provides a quick and accurate report on patients' attitudes to their own predicaments.

But PRISM is more than a passive recording device – it can actually help patients to get better. Büchi and Sensky show how patients can improve their ability to cope with chronic pain and depression by learning how to play PRISM in their heads, mentally 'separating' the red 'illness' disk from the yellow 'self' disk. In a variation called 'PRISM+', other disks can be brought in to represent partners, family, career and so on. This helps patients, disoriented by the disruption of chronic illness, to regain some perspective on their lives and restore a measure of control.