Confirming my suspicions that when it comes to severe asthma, we are all mostly just faking it, this consensus guideline from the European U-BIOPRED public/private consortium points out how little we really know about this complex and variable illness. There are a couple of helpful tables and algorithms here to help you make sure you've ruled out or treated any comorbid/contributing conditions. Interestingly, fundoplication may be helpful for many with GERD believed to be producing asthma symptoms, unresponsive to proton pump inhibitors.
Otherwise, this document points out that we are still at the stage of trying to define what severe asthma is and identify meaningful phenotypes. They propose a few, based on clinical patterns and eosinophilia. Still a lot to be learned about this complex illness, they remind us.
Bel et al. Diagnosis and definition of severe refractory asthma: an international consensus statement from the Innovative Medicine Initiative (IMI). Thorax 2011;66:910-917.