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NNTs used in decision-making in Chronic Pain Management

Making decisions about the benefits of psychologically-based treatments of medical problems is not easy, and especially difficult to compare with other treatments and to measure relative benefit and cost. Patients whose pain has proved intractable to all reasonable medical and other interventions are chronic consumers of health care - GP or hospital clinic time, analgesic and psychotropic drugs, repeated admissions and sometimes surgery. If rehabilitation treatment enables these patients to carry on more satisfying lives with minimum medical help, how can it be most effectively and economically offered? The use of NNTs may be a start in making decisions of clinical and cost effectiveness.

The study

With a grant from the King's Fund, we compared four-week inpatient treatment (patients looked after themselves in hostel accommodation and went home at weekends) with eight-week half-day outpatient treatment. Pain management methods were taught by the same staff team; they incorporated fitness training, planned increases in activity, activity scheduling, drug reduction, relaxation and cognitive therapy [1,2]. Patients were randomised (dice-throw) to treatment group and controls; there were 41 inpatients, 42 outpatients and 31 waiting list controls.

Outcome measures

Patients listed the treatments they had required for pain before the treatment started, four weeks after the end of treatment and during the year following the end of the intervention - prescribed drugs, a variety of medical and surgical interventions, physiotherapy, acupuncture, osteopathy or chiropractic. A number of physical and psychological measures and drugs taken were also used as outcome measures.


The intention-to-treat analysis (including the 20% who dropped out during treatment or during the period up to the one year to follow up) showed that waiting list controls showed no change, but that treatment both as inpatients and outpatients resulted in benefit.

This is good enough, but most interesting was the consistent pattern of NNTs favouring inpatient treatment. At one year after the end of treatment, results favoured inpatient over outpatient treatment, with the NNTs shown in the table.
  • For every three patients treated as inpatients rather than outpatients, one patient fewer was taking analgesic or psychotropic drugs.
  • For every four patients treated as inpatients rather than outpatients, one patient fewer sought additional medical advice in the year after treatment.
  • For every five patients treated as inpatients rather than outpatients, one patient more had a ten-minute walking distance improved by more than 50%.
  • For every six patients treated as inpatients rather than outpatients, one patient fewer was depressed.


The use of NNTs in this complicated area has helped to clarify results without the dubious combination of diverse outcomes. The advantages, both of either treatment over nothing, and of inpatient over outpatient treatment, are consistent. The costs of treatment (£2,000 for each inpatient, £450 for each outpatient) are known. Now drug [3] and medical intervention savings can be estimated and net costs or savings balanced against benefits to patients and carers through improved activity and mood.

While return to work is rare in a group of middle-aged manual or semi-skilled workers, especially those who have had pain for an average of 10 years and have been out of work for little less, there are still benefits not only to the individuals, but also to the community, in finding how best to measure their quality of life. NNTs may be the key.
Amanda C de C Williams
INPUT, St Thomas' Hospital, London


  1. CE Pither, MK Nicholas. Psychological approaches in chronic pain management. British Medical Journal 1991 47: 743-61.
  2. ACdeC Williams. Inpatient management of chronic pain. In M Hodes & S Morley (eds) Psychological treatment in disease and illness. London: Gaskell Press (1993).
  3. CE Pither, JA Ralph. Limiting the drugs list - behavioural treatment not drugs for chronic pain. British Medical journal 1993 306: 1687-8.

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