Editing Asthma (section)

===Others===
The [[methacholine challenge test|methacholine challenge]] involves the inhalation of increasing concentrations of a substance that causes airway narrowing in those predisposed.<!-- <ref name=M38/> --> If negative it means that a person does not have asthma; if positive, however, it is not specific for the disease.<ref name=M38/>

Other supportive evidence includes: a ≥20% difference in [[peak expiratory flow rate]] on at least three days in a week for at least two weeks, a ≥20% improvement of peak flow following treatment with either salbutamol, inhaled corticosteroids or prednisone, or a ≥20% decrease in peak flow following exposure to a trigger.<ref>{{cite journal | vauthors = Pinnock H, Shah R | title = Asthma | journal = BMJ | volume = 334 | issue = 7598 | pages = 847–50 | date = April 2007 | pmid = 17446617 | pmc = 1853223 | doi = 10.1136/bmj.39140.634896.BE }}</ref> Testing peak expiratory flow is more variable than spirometry, however, and thus not recommended for routine diagnosis.<!-- <ref name=NAEPP2007p59/> --> It may be useful for daily self-monitoring in those with moderate to severe disease and for checking the effectiveness of new medications.<!-- <ref name=NAEPP2007p59/> --> It may also be helpful in guiding treatment in those with acute exacerbations.<ref name=NAEPP2007p59>{{harvnb|NHLBI Guideline|2007|p=59}}</ref>