Patient groups who are classified as immunocompromised include those undergoing chemotherapy, those taking glucocorticosteroids and those with acquired immunodeficiency syndrome (AIDS). Patients who are immunocompromised are more susceptible to the risks of cross infection, their defence immune system is not adequate to prevent infection.

These individuals need to be tested in an environment which is low risk for cross infection. Given that at the end of each day surfaces are cleaned and an overnight sterilisation of equipment components is undertaken, the safest time of day to perform spirometry for this group is the first test of the day. If an early appointment is not possible, aseptic techniques must to be employed to reduce the likelihood of cross-infection.