Before the biopsy is performed it is important to thoroughly evaluate the patient for:-

Concomitant medication / illness
Any drug allergy
Past history of bleeding / clotting problems
If pregnant Biopsy should not be performed.
If patient shows symptoms of :
1. Bullae (Enlarged alveoli associated with emphysema)
2. Presence of cysts
3. Severe Hypoxia (Insufficient concentration of oxygen in blood)
4. Pulmonary hypertension
Primary lung diseases [cor pulmonale]
Routine blood investigations
Chest X-ray - To locate the exact biopsy site
Platelet counts is commonly done to check if the individuals bleeding and clotting parameters are within normal limits. For those with counts lower than 50,000/cubic mm, a platelet transfusion would be required before the biopsy.
An arterial blood gas and a pulmonary function test may also be done.