Sometimes additional tests, such as a chest x-ray, TB skin test, blood test, pulmonary function test, or even bronchoscopy, may be needed.Diagnosing the cough is very important if the cough makes it difficult for your child to breathe, if you suspect your child may have inhaled some food or other object, if there are intense spasms of coughing, if your child otherwise seems ill (as with a high fev