RAD Dx vs Asthma

What is the criteria to determine the differential diagnosis between RAD and asthma and at what time does a patient's status change from an initial diagnosis of RAD over to asthma?  Thank you!

[National Jewish Health]

Reactive airways disease (RAD) is really more a condition or characteristic of the airways.  Hyperreactive airways disease would be a more accurate description of the condition.  The airways of all people will constrict in response to noxious stimuli, for example smoke from a burning building.  The airways of individuals with RAD are just more sensitive to stimuli, such as chemical, infectious, or allergic, than the rest of us.  Being more sensitive, also known as hyperreactive, they are more likely to constrict, constriction being a prime feature of asthma.

And so, RAD is but one characteristic of asthma.  Some doctors use the term RAD rather than the diagnosis of asthma, especially with young children when it is not always possible to be certain of that diagnosis, because they are too young to follow directions well enough to perform spirometry, a simple breathing test used to determine if asthma is the problem.

One sign of the transition from RAD to asthma is when the airways seem to constrict spontaneously; that is, without any obvious noxious substance, clearly being the cause.

Hope this helps.