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For each therapy and for each of the clinically relevant outcomes, the available evidence was summarised as shown in the following table:
Strong evidence for effectiveness
3+ |
Systematic review finding a statistically significant and clinically important effect (without significant heterogeneity)
OR
More than one randomised controlled trial finds a statistically significant and clinically important effect and there are no equivalent trials showing absence
of effect |
Probably effective
2+ |
More than one controlled trial available. A majority, but not all, of which show a statistically significant and clinically important effect |
Possibly effective
1+ |
One controlled trial available shows a statistically significant effect |
Equivocal evidence of effect
+/- |
Randomised or non-randomised clinical trials yield conflicting results, demonstrated effects are probably not clinically important |
Possibly ineffective
1- |
One small controlled trial available shows no significant effect |
Probably ineffective
2- |
More than one controlled trial available. A majority, but not all, of which exclude a clinically important effect (absence of effect)
OR
One large controlled trial excludes a clinically important effect |
Strong evidence of lack of effect
3- |
Systematic review excludes a clinically important effect (without significant heterogeneity)
OR
More than one randomised controlled trial excludes a clinically important effect |
Insufficient evidence
0 |
Available evidence does not meet the above criteria |
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Results
The results of this review of effectiveness are summarised in the accompanying table. In addition, the table describes the patient group in which effectiveness was assessed; that is, the age group, the level of asthma control of the subjects, and their concomitant therapy. In particular, it should be noted that there are difficulties in translating effects observed with treatment of adults to those that could be expected when the same treatment is applied to children.
The table also cites evidence of adverse effects and other safety considerations, such as potential interactions with other treatments, which are relevant to the therapies. Additional information for medicinal therapies listed in this table was gained by searching the databases listed at the end of this paper.
Therapies for which there is insufficient evidence for all clinically relevant outcomes of asthma are not included in the table.
Methodology
Systematic reviews of the literature were undertaken for each of the complementary therapies that were identified as being of interest. The following databases were searched: Medline, Embase, Cinahl, Amed (Allied and Complementary Medicine database, www.bl.uk/services/information/amed.html), and
the Cochrane Library (www.update-software.com/clibng/cliblogon.htm), Cochrane Central Register of Controlled Trials
and the Cochrane Database of Systematic Reviews). For the Cochrane Databases, a simple search strategy combining the therapy descriptor(s) with the term ‘asthma’ was used. The following methodological filters, adapted from those recommended by Haynes et al.1 for the purpose of identifying citations relevant to therapy2, were used in the other database:
Medline
randomised controlled trial.pt. OR dt.fs. OR tu.fs. OR random$.tw.
Embase
randomised controlled trial/ OR dt.fs. OR random$.tw.
Cinahl
dt.fs. OR tu.fs. OR random$.tw.
Amed
random$.tw.
Each search combined terms for the therapy under consideration, the term ‘asthma’, and the methodological filter. Searches were limited to those articles with English language abstracts in which human subjects were studied.
Available evidence was ranked according the following levels of evidence(3):
I Evidence obtained from a systematic review of all relevant randomised trials.
II Evidence obtained from at least one properly designed randomised trial.
III Evidence obtained from other non-randomised controlled trials.
Abstracts reporting lower levels of evidence (non-systematic reviews, uncontrolled studies, case series, case reports or expert opinion) were excluded. Only those studies reporting one or more of the clinically relevant outcomes, described in the section ‘Aims of treatment for people with asthma’ in this paper, were included.
Where Level I evidence for the effect of a therapy was available, further evidence was not considered unless it was published after the last update of the systematic review or it reported outcomes not encompassed by the systematic review. Where Level II evidence was available, Level III evidence was not considered unless it was published later or reported outcomes not included in the randomised controlled trial. Where conflicting evidence
at the same level was reported, higher quality studies were given precedence.
Content Updated March 2005
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