Self-employed? Or being diddled?
Peak flow meters do not in general improve guided self-management for children with asthma, says Professor Mike Silverman
The greatest practical challenge in the management of any chronic disease is improving patient adherence to therapy. The argument goes that informing parents and children and giving them the right tools allows them to reduce the adverse impacts of asthma on daily life and thereby motivates them to comply.
Guided self-management comes as a package a written plan, based on action points (determined by symptoms or PEF), with specific instructions on how to increase or decrease treatment, all reinforced by some sort of educational programme. Until recently, it was unclear which components were effective. An analysis of 26 randomised controlled trials (RCTs) of self-management in adults1 showed plans that permitted adjustment of both inhaled steroid and oral steroid doses reduced morbidity more than those that allowed variation in only one drug.
There was no overall benefit to adding PEF monitoring to symptom-based self-management, but if included in the plan, PEF action points based on the 'personal best' value were more effective than those based on 'percentage predicted'.
Does PEF monitoring help
children with asthma?
This sort of analysis of RCTs has not been carried out for childhood asthma, but a study by my research group last year2 addressed the issue of PEF monitoring.
The Leicester-based research group carried out a randomised trial in 90 schoolchildren with asthma, recruited mainly in primary care. They were on step 2 or 3 of the UK Asthma Guidelines.
After a four-week run-in, 90 children were randomly assigned to receive either PEF and symptom-based management or symptom-based management alone for 12 weeks. A 'traffic light' system was designed around the 1995 version of UK Asthma Guidelines, with action points for PEF of 70 per cent personal best (double inhaled steroids dose) and
50 per cent personal best (start oral steroids). Ingeniously instead of a standard PEF meter, children were issued with a small electronic recording spirometer.
Children in the PEF group could use it like a PEF meter and see their PEF value displayed, while for the control group, the result was simply stored away in a memory chip for later analysis. The device also allowed FEV1 to be recorded and to check spirometric quality.
The trial came to several useful conclusions:
(i) PEF measurements provided no advantage over symptom-based self-management, with respect to symptom scores, quality of life, additional steroid therapy, GP emergency visits or lung function.
(ii) PEF did not fall to 70 per cent (the first action point) during episodes which were sufficiently severe to require increased therapy.
(iii) FEV1 was no more sensitive than PEF.
(iv) Children's compliance with PEF measurement fell steadily with time. By the end of the trial, compliance had fallen to 58 per cent.
How valid is the main conclusion, that there was no benefit to routine PEF monitoring in this group of children? Several potential drawbacks are worth considering.
(i) Perhaps by providing careful education to motivate families in the context of a trial, the skills of both groups were enhanced sufficiently to reduce any potential benefit of PEF measurement. If so, the conclusion remains that the added cost and complexity of PEF monitoring is not worthwhile.
(ii) This was a stable and relatively mild group of children. Could PEF meters be useful in more severe or unstable groups? Probably not since that group includes children whose compliance is often an issue. Putting more demands on the family is unlikely to help in practice.
(iii) Were the PEF action points
(70 per cent and 50 per cent) appropriate? It has been suggested 80 per cent might be more appropriate. However the mean PEF during the study was only 83 per cent best. A threshold of 80 per cent would have led to overtreatment of many stable, symptom-free children.
(iv) Was the UK Asthma Guidelines advice appropriate? The advice to 'double your inhaled steroid preventer' was current at the time.
It is now clear that the advice doesn't work for adults (and probably for children too)3,4. So the trial may have been based on an ineffective intervention. But this does not detract from the fact that symptoms were still more sensitive than a PEF threshold of 70 per cent.
Should PEF meters
Not yet. They have a role in diagnosis, determining level of control and
possibly for selected individual management.
Distinguishing other causes of airway obstruction from asthma is best done by spirometry. PEF measurement before and after bronchodilator (four puffs salbutamol or terbutaline by spacer) can be useful in diagnosis.
Lack of variation in PEF during two weeks of twice-daily home monitoring should raise doubts about a diagnosis of asthma in a symptomatic child.
Judging the effectiveness of changes in therapy on asthma control may be enhanced by a two- to four-week PEF diary.
For selected cases ('under-perceivers') a PEF meter may give the necessary guidance to start a course of oral
steroids during an acute attack of asthma. This pragmatic approach has yet to be proved.
So to sum up, selectively used, to answer specific questions, in some schoolchildren with asthma, PEF meters can help. But blanket advice to monitor PEF is ineffective.
· PEF meters do not improve
self-management for children in most cases
· Symptoms are the most
sensitive marker for increasing therapy
· PEF meters may be useful in selected patients
· PEF meters can also be used in making a diagnosis and assessing control
1 PG Gibson and H Powell. Written action plans for asthma: an evidence-based review of the key components.
2 Wensley D, Silverman M. Peak flow monitoring for guided self-management in childhood asthma: a randomised controlled trial. Am J Respir Crit Care Med. 2004;170:606-12
3 FitzGerald JM et al. Canadian Asthma Exacerbation Study Group.. Doubling the dose of budesonide versus maintenance treatment in asthma exacerbations.
4 Harrison TW et al. Doubling the dose of inhaled corticosteroid to prevent asthma exacerbations: randomised controlled trial. Lancet. 2004;363:271-5
Mike Silverman is professor of child health, department of infection, immunity and inflammation, Leicester Medical School, University of Leicester