Greenwich asthma study

Greenwich asthma study

Authors’ reply

The Asthma Resource Centre was set up by the Primary Care Development Fund to improve the health of people with asthma living in Greenwich. We evaluated whether the centre had achieved its objectives. If it had done so and cost effectively it would have been an excellent model for other districts. At the outset the evaluation team was divided about whether the project was likely to succeed.

We did not measure the efficacy of the asthma nurses but their effectiveness. The idea behind the centre was to show that similar schemes could be applied across a district beyond the confines of a localised research environment. A key prerequisite for success was the nurses’ ability to find and contact patients who would benefit.

The centre might have been more successful if it had targeted patients with severe asthma. This targeting was not part of the centre’s protocol or a stipulation of other programmes such as the chronic disease clinics funded nationally in primary care. We did not suggest that doctors would be more effective than nurses in educating patients with asthma but that the nurses might have been more effective if the general practitioners had been more active in the project.

Health related quality of life is a suitable primary outcome because it applies to all patients with asthma, responds to change, and summarises the benefit perceived by patients. A small change would have shown that the programme was worth while, which is why the study was so large. Most of the patients did not have trivial disease: 43% had symptoms at least three times a week and 59% were woken by symptoms at least once every month. ⁽¹⁾ To exclude patients who were not receiving treatment would have been wrong as some of these patients might have benefited the most. We tested separately whether those who had the worst quality of life had benefited, and they had not.

The study had the power to detect changes in prescribing practice, but these changes were seen equally in the intervention and control practices. This alone shows that there are more effective ways of changing prescribing.

In the new age of primary care groups general practitioners need to distinguish between efficacy and effectiveness. The government should continue to search for effective programmes, which may include asthma nurses. It should implement on a large scale only programmes that are cost effective when implemented in representative practices. More research should be dedicated to identifying efficient methods of finding and accessing those who can benefit from the programmes.

In reply to Parnell and Cook’s letter, published last year, ⁽²⁾ the nurses in the control and intervention practices were matched at the beginning of the trial for expertise in asthma education. Few practice nurses in either group at that time had the diploma from the National Asthma Training Centre.

To say, "it seems unlikely that the control group was untainted" is misleading. ⁽²⁾ This implies that the control group was tainted by the intervention, which is most unlikely. Both groups were equally affected by the other initiatives that were being taken locally and nationally at the time (as shown by the analysis). The question being tested, however, was whether an asthma resource centre such as that in Greenwich would be more effective than any other initiatives. We conclude that other factors at this time were much more effective, at least in increasing the prescription of steroids.

The evaluation study compared quality of life in those aged 16-50; the nurses saw only 17% of the patients in this age group with an estimated diagnosis of asthma from the respiratory questionnaire but 26% of all patients. The evaluation was conducted on the basis of intention to treat, and the failure to reach 83% of the treatment group is an important result. We agree with Parnell and Cook’s implication that this made the success of the intervention unlikely, but the sample size was not small. It was large and representative of those that the trial was intended to help.

Because of limitations of space we did not describe in detail the work done in secondary care. Patients admitted to hospital from the intervention group practices were either seen on the ward by the nurse specialists or notified to the practice nurses. Patients from the intervention group practices seen in accident and emergency departments were notified to their practice nurse. An audit of this recall system over the last three months of the study showed that the proportion of patients who were reviewed in primary care was disappointingly small. The project was led from secondary care by the local respiratory physician (JW) and by nurse specialists who were based in the local hospital but worked mostly in primary care.

U N Premaratne
consultant in communicable disease control

Bexley and Greenwich Health Authority, Bexleyheath, Kent DA7 6HZ
J A C Sterne
senior lecturer

Department of Epidemiology and Community Medicine, University of Bristol, Bristol BS8 2PN

P G J Burney
Professor

Department of Public Health Sciences, King’s College London, Capital House, London SE1 3QD
Peter.burney{at}kcl.ac.uk

G B Marks
research fellow

Institute of Respiratory Medicine, University of Sydney, New South Wales 2006, Australia
J R Webb consultant physician

Greenwich District Hospital, London SE10 9HE

1. Marks GB, Burney PGJ, Premaratne UN, Simpson J, Webb J. Asthma in Greenwich, UK: impact of the disease and current management practices. Eur Respir J 1997;10:1224-9.
2. Parnell H, Cook NT. The Greenwich asthma study. BMJ 1999;319:709. (11 September.)