Table 2

Evidence-based statements extracted from international guidance used to assess compliance with evidence-based recommendations.

Statement

Evidence-base

Rationale for categorization


Secondary prevention-removal of pets from the home

Uncertain

"Complete avoidance of pet allergens is impossible [...] Although removal of such animals from the home is encouraged, even after permanent removal of the animal it can be many months before allergen levels decrease and the clinical effectiveness of this and other interventions remains unproven." [7] "The reported effects of removal of pets from homes are paradoxical, with either no benefit for asthma, or a potential for continued high exposure to induce a degree of tolerance." [5] [EPR-3 suggests that animal removal could be considered but rates the evidence Grade D which reflects panel consensus only] [6]


Secondary prevention-fungal allergen avoidance and control measures

Uncertain

"Air conditioners and dehumidifiers may be used to reduce humidity to levels less than 50% and to filter large fungal spore. However, air conditioning and sealing of windows have also been associated with increases in fungal and house dust mite allergens." [7] "Although fungal exposure has been strongly associated with hospitalisation and increased mortality in asthma, no controlled trials have addressed the efficacy of reduction of fungal exposure in relation to control of asthma." [5] "The Expert Panel recommends consideration of measures to control indoor mold [...] but the relative contribution of fungi, house-dust mites or irritants [to asthma symptoms] is not clear." [6]


Secondary prevention-cockroach avoidance and control measures

Uncertain

"[Measures for cockroach control] are only partially effective in removing residual allergens." [7] "Cockroach allergy is not a common problem in the UK and studies of attempts to avoid this allergen elsewhere have produced conflicting results." [5] [EPR-3 recommends cockroach control if the patient is sensitive to cockroaches]. [6]


Secondary prevention-cessation of active smoking

Beneficial

"Secondhand smoke increases the frequency and severity of symptoms in children with asthma." [7] "Direct or passive exposure to cigarette smoke adversely affects quality of life, lung function, need for rescue medications for acute episodes of asthma and long term control with inhaled steroids." [5] "[Smoke exposure] is associated with increased symptoms, decreased lung function, and a greater use of health services among those who have asthma." [6]


Secondary prevention-avoidance of passive smoking

Beneficial

"Asthma patients who smoke and are not treated with inhaled glucocorticosteroids, have a greater decline in lung function than asthmatic patients who do not smoke." [7] "Direct or passive exposure to cigarette smoke adversely affects quality of life, lung function, need for rescue medications for acute episodes of asthma and long term control with inhaled steroids."[5] "[Smoke exposure] is associated with increased symptoms, decreased lung function, and a greater use of health services among those who have asthma." [6]


Secondary prevention-avoidance of exposure to air pollution

Uncertain

"Avoidance of unfavourable environmental conditions is usually unnecessary for patients whose asthma is controlled." [7] "While it might seem likely that moving from a highly polluted environment might held, in the UK, asthma is more prevalent in 12-14 year olds in non-metropolitan rather than metropolitan areas." [5] "Clinicians [should] advise patients to avoid, to the extent possible, exertion or exercise outside when levels of air pollution are high." [6]


Secondary prevention-immunotherapy for a defined allergen

Beneficial

"Appropriate immunotherapy requires the identification and use of a single well-defined clinically relevant allergen." [7] "Immunotherapy can be considered in patients with asthma where a clinically significant allergen cannot be avoided." [5] "Immunotherapy [should] be considered for patients who have persistent asthma if evidence is clear of a relationship between symptoms and exposure to an allergen." [6]


Secondary prevention-weight reduction in obese patients

Beneficial

"Weight reduction in obese patients with asthma has been demonstrated to improve lung function, symptoms, morbidity and health status." [7] "One randomised parallel group study has shown improved asthma control following weight reduction in obese patients with asthma." [5] "Obesity has been associated with asthma persistence and severity in both children and adults. [...W]eight loss in adults resulted in improvement in pulmonary mechanics, improved FEV1, reductions in exacerbations and courses of oral corticosteroids and improved quality of life." [6]


Secondary prevention-seasonal influenza vaccination

Uncertain

"Patients with moderate to severe asthma should be advised to receive an influenza vaccination every year [...] however routine influenza vaccination of children and adults with asthma does not appear to protect them from asthma exacerbations or improve asthma control." [7] "Immunisations should be administered independent of any considerations related to asthma." [5] "[We recommend] that clinicians consider inactivated influenza vaccination for patients who have asthma [...] however the vaccine should not be given with the expectation that it will reduce either the frequency or severity of asthma exacerbations during the influenza season." [6]


Statements were extracted from the UK BTS/SIGN, US EPR-3 and international GINA guidelines.

'Uncertain' was used when either all three guidelines agreed that the evidence base was uncertain or where the advice given by the guidelines differed. We retained only topics discussed by all three sets of guidelines.

Huckvale et al. BMC Medicine 2012 10:144   doi:10.1186/1741-7015-10-144

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