Context: Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in one second (FEV1), and peak expiratory flow rate. Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic), based on whether symptoms are precipitated by allergens (atopic) or not (non-atopic). While asthma is classified based on severity, at the moment there is no clear method for classifying different subgroups of asthma beyond this system. Finding ways to identify subgroups that respond well to different types of treatments is a current critical goal of asthma research.

Question: How is asthma clinically classified?
Answer: according to the frequency of symptoms, forced expiratory volume in one second (FEV1), and peak expiratory flow rate

Question: How else is asthma classified?
Answer: as atopic (extrinsic) or non-atopic (intrinsic)

Question: When asthma is caused by allergens that is called what? 
Answer: atopic

Question: What  is asthma usually classified based on?
Answer: severity

Question: What is a important goal of asthma research?
Answer: Finding ways to identify subgroups that respond well to different types of treatments

Question: How are allergen subgroups classified?
Answer: Unanswerable

Question: What are two other ways allergen subgroups may be classified?
Answer: Unanswerable

Question: What data is allergen subgroup classification based on?
Answer: Unanswerable

Question: Is there a method for classifying allergen subgroups beyond the existing system?
Answer: Unanswerable

Question: What is the main goal of allergen subgroup research?
Answer: Unanswerable