Thanks for your query.
Normal PFT doesnot mean that you dont have asthma
The diagnosis of asthma is more of clinical than PFT finding
As your doctor found spasm and your symptom has a seasonal variation brochial asthma is most likely
On long term basis neither deriphyllin
systemic steroid is hardly used in asthma unless there is exacerbation.
The drug deriphyllin also has many side effects
main drug is inhalational corticosteroids
on long term basis salmeterol-fluticasone is appropriate
then if not controlled with these two then montelukast
or deriphyllin may be added