Question: One of our patients came in experiencing exacerbation of their asthma due to acute bronchitis from a parainfluenza virus infection. How to I properly sequence the codes? Wisconsin Subscriber Answer: Sequencing is important when coding for asthma, and as you already have noticed, parent code J45.- (Asthma) features instructions to use an additional code to identify certain triggers of asthma exacerbation. The ICD-10 guidelines also say to list the asthma code first, followed by the code for the trigger. Therefore, for this particular case, you should assign J45.41 (Moderate persistent asthma with (acute) exacerbation) first, and then J20.4 (Acute bronchitis due to parainfluenza virus) as the second code.