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Antibiotic prescribing dilemmas: striking the right balance

A recent study linked a rise in pneumonia deaths to reduced antibiotic prescribing – Dr Nicola Baker and Dr Tim Weller advise on appropriate prescribing

Key points

lReducing antibiotic prescribing, in an attempt to curb the rise in antimicrobial resistance, is a national priority.

lA study1 raised fears this may be linked to a rise in mortality – the solution is to use antibiotics appropriately for those patients most likely to benefit.

lPneumonia is unlikely in patients without focal chest signs or systemic features of infection and antibiotics can be safely withheld.

lPatient pressure is a factor in oversubscribing of antibiotics – delayed prescriptions offer a partial solution.

1. Key principles of appropriate antibiotic prescribing

'The cost-effective use of antimicrobials which maximises clinical therapeutic effect while minimising both drug-related toxicity and the development of antimicrobial resistance' WHO, 2001

lOnly prescribe antibiotics when there is evidence of bacterial infection

lDo not prescribe antibiotics for self-limiting infections

lAlways prescribe an antibiotic with the narrowest spectrum of activity that will cover the most likely bacterial pathogen(s)

lAlways give the shortest duration of therapy necessary

lAlways use a sufficient dose to ensure activity at the site of infection but minimise toxicity

SMAC recommendations for appropriate antibiotic use in

primary care:

lNo prescribing of antibiotics for coughs and colds

lNo prescribing of antibiotics for viral sore throats

lLimit prescribing for uncomplicated cystitis in women to three days

lLimit prescribing of antibiotics over the telephone to exceptional cases

2. Sources of guidance for antibiotic prescribing in

respiratory tract infections

Health Protection Agency

Management of infection guidance for primary care: draft for consultation and adaptation. Provides brief details of the antibiotic management of all types of infections. www.hpa.org.uk

PRODIGY

Comprehensive evidence-based guidelines for the diagnosis and management of sore throat and chest infection. Also provides patient information leaflets for patient use. www.prodigy.nhs.uk

Scottish Intercollegiate Guideline Network

Comprehensive evidence-based guidance for the community management of sore throat and lower respiratory tract infections. www.sign.ac.uk

British Thoracic Society

Guidelines for the management of community acquired pneumonia in adults. Extensive guidance on assessment and management of patients in hospital and community. www.brit-thoracic.org.uk

3. Guidelines for the clinical

assessment of respiratory tract

infection in the community

Sore throat: Centor criteria

Presence of three of the following four clinical features in an unwell patient is highly predictive of group A ß-haemolytic streptococcal infection and a higher risk of complications:

lHistory of fever

lAbsence of cough

lCervical adenopathy

lPurulent tonsillitis

LRTI

The BTS definition of pneumonia in the community includes patients with:

lSymptoms of lower respiratory tract infection (cough plus at least one other symptom, such as dyspnoea, chest pain, sputum)

lNew focal chest signs on examination

lAt least one systemic feature (temperature >38°C, myalgia, shivers, night sweats)

lNo other explanation for the illness

References

1. Price DB et al. Community acquired pneumonia mortality: a potential link to antibiotic prescribing trends in general practice. Resp Med 2004;98:17-24

2. Del Mar CB et al. Antibiotics for sore throat (Cochrane review).

In: The Cochrane Library, Issue 2, 2004

3. Anthonisen NR et al. Antibiotic therapy in exacerbations of chronic obstructive pulmonary disease. Annals Intern Med 1987;106:196-204

4. Little P et al. Antibiotic prescribing and admissions with major suppurative complications of respiratory tract infections: a data linkage study.

Br J Gen Pract 2002;52:187-93

5. Fahey T et al. Quantitative systematic review of randomised controlled

trials comparing antibiotics with placebo for acute cough in adults.

BMJ 1998;316:906-10

6. Dowell J et al. A randomised controlled trial of delayed antibiotic prescribing as a strategy for managing uncomplicated respiratory tract infection in primary care. Br J Gen Pract 2001; 51:200-5

7. Scottish Intercollegiate Guidelines Network. Community Management of Lower Respiratory Tract Infection in Adults. 2002. Available at: www.sign.ac.uk

GP academic whose research sparked controversy

Research needed on link between fall in scripts and rise in deaths

Professor David Price led the study that linked the fall in antibiotic prescribing with a rise in pneumonia mortality.

He maintains more research is needed.

GPs have been at the forefront of efforts to curb antimicrobial resistance in recent years by reducing the number of antibiotic prescriptions they write. Total antibiotic prescribing in England fell by almost a quarter in the second half of the 1990s, from 45 million to 34 million prescriptions a year. A study in the West Midlands showed the largest falls were for lower respiratory tract infection (LRTI), followed by upper respiratory tract infections and throat infections.

The decline in antibiotic prescribing for LRTI is of potential concern, given the difficulties facing GPs trying to distinguish self-limiting LRTI from pneumonia. With this in mind, I brought together a group of like-minded researchers from general practice, public health and respiratory medicine to ask whether these declines in prescribing have had an effect on patient outcomes.

Our study compared trends in antibiotic prescribing for LRTI with changes in pneumonia mortality between 1993 and 2000. We chose a 12-week analysis period each winter, in which the majority of pneumonia deaths regularly occur. To take account of deaths from pneumonia that occur throughout the year, summer pneumonia mortality was subtracted, to calculate what is known as the 'winter excess'. Yearly variations in influenza affect pneumonia mortality, and so were taken into account.

Our study showed antibiotic prescribing for LRTI declined by almost a third from its peak in the winter of 1995/6. Winter excess pneumonia mortality increased by 50 per cent over the same period, given constant influenza levels. In a statistical analysis of the major influences on pneumonia mortality, antibiotic prescribing had a significant effect. This was second only to the well-known effect of influenza, and well behind any steady year-on-year changes due to changes in health care or an ageing population.

The Specialist Advisory Committee on Antimicrobial Resistance took issue with our analysis, and the use of pneumonia mortality in particular. Yes, death certification data is not 100 per cent reliable, but we have no reason to believe it has changed dramatically over the period of our study. More importantly, it is an endpoint that is important to GPs – and their patients.

Our choice of 12-week winter period was also questioned, but when this was extended to 16 or 20 weeks (almost half a year) the relationship we observed between pneumonia mortality, influenza incidence and antibiotic prescribing still held.

The committee has raised a number of other concerns in a letter to the editor of Respiratory Medicine, which we have answered with reference to our original paper.

We have been at pains to point out the relationship we observed may be no more than a statistical association and, as such, our findings should be interpreted cautiously. Our aim has been to raise awareness that the long-term effect of declines in antibiotic prescribing for LRTI on patient outcomes is far from clear, to stimulate further research.

Large-scale prospective studies are needed to confirm – or disprove – our findings, although support for these has not yet been forthcoming. The existing evidence on which GPs can base their decisions when treating LRTI in the community is weak. Only with further research can we be sure we are prescribing antibiotics for these potentially life-threatening infections both effectively and appropriately.

David Price is professor of primary care respiratory medicine at the University of Aberdeen and a part-time GP in Norwich

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