When you look up Asthma in the Index, and follow it down to "with rhinitis, allergic" it refers you to a combination code of 493.00. So basically if the doctor is coding Asthma 493.90 and also Allergic Rhinitis (477.xx), then you would use the combo code 493.00 and drop the 477.xx Allergic Rhinitis, because the addition of "allergic rhinitis" (477.xx) makes the asthma "extrinsic'. Extrinsic asthma means there is an allergen, such as pollen, pet dander and mold, etc., that is triggering the asthma. In contrast, Intrinsic Asthma means asthma symptoms are triggered by factors not related to allergies, such as laughing, coughing, contact with chemicals like cleaning agents and cigarette smoke, exercising, etc. Even if the physician is coding 493.00 Extrinsic Asthma and also Allergic Rhinitis then again, you would use the combo code 493.00 and drop the Allergic Rhinitis. If however, the physician uses the phrase "Allergic Asthma" (493.90) without stating 'Allergic Rhinitis' then the only way you would be able to use a combo code of 493.00, would be if he actually stated the allergen that was causing it to be allergic asthma within the documentation. Just remember, for it to be considered Extrinsic, there has to be an allergen or the phrase "allergic rhinitis" stated within the documentation.
