Should a child with copd have a blood test, to rule out alpha 1 antitrypsin deficiency?

Yes: COPD is extremely rare in children. Alpha 1 antitrypsin deficiency is a known cause of COPD or emphysema. The onset of lung disease is uncommon before early adulthood. Protein replacement therapy is available to treat this disorder if causing copd/emphysema.

Probably...: If a child has copd, and not asthma, then an alpha-1-anti trypsin level probably ought to be checked. The child needs to have an evaluation so the proper diagnosis and treatment can be given!