Hi Valerie,
While I don't want to second guess your doctor, I would like to make a comment or two. I think when your own instinct is telling you something doesn't sit right, it might be prudent to get a second opinion before taking an invasive action. Sure, it is possible the bronch may reveal something that couldn't have been identified through other means. But on the other hand, my question to the doctor is this: Is it possible that another culture would show something BEFORE be do a bronch?
I can only tell you how my doctor handles my coughs. Which may be entirely different from Noah's of course. My doctor does not do bronchs as a matter of routine, because there is a possibility of introducing new bugs into the lungs. Equipment is not always sterilized properly. So up until now, I haven't had a bronch and hope never to have to have one. My doctor has been able to identify my problems without the use of them.
You said Noah's IGG test was a little elevated. That test measures the most common antibodies in the body which fight bacterias AND viruses. So if it is a virus, an antibiotic would have no effect on it.
There is another test called an IgE blood test which also measures antibodies, but these cause the body to react against, pollen, fungus, spores, animal dander, etc. It can be used as a clue to whether allergies are causeing inflammation which causes a lot of unexplained coughs. I say clue, because the test can even be negative, and "allergens" or irritants can inflame the already hypersensitive airways of people with lung problems. Noah is also old enough to have allergy skin tests -- which may also provide clues. Again, they can't test for everything, but this is a start. And there are no tests for chemical sensitivities, but this can also cause exacerbations. Was Noah exposed to anything 3 weeks ago? New school, paint job, vacation, new furniture, etc.?
The other question I would ask the doctor is Noah's throat red, eardrums red and swollen? How does his chest sound? All clues towards inflammation if you can't find any bacterial, fungal, or viral reasons for his increased symptoms.
At any rate, I would investigate this further with other opinions.