Table 1.

ICD-9 codes used as diagnoses of interest

Definition of COPD diagnosis
One or more visits with any of following ICD-9 codes in 2006–2007
491.2xx
492xx
496
Respiratory illness visit codes
Probable COPD exacerbations
Wheezing	786.07
COPD exacerbation	491.21
Bronchitis	466.xx or 490.xx
Pneumonia/pneumonitis/influenza	480–488
Burst of oral steroids	From e-prescribing data
Emergency room or hospitalization for respiratory event	From local codes developed in billing for site of visit
Possible COPD exacerbations
Coughing	786.2.xx
URI	462.xx or 461.xx or 465.xx

Abbreviations: COPD, chronic obstructive pulmonary disease; URI, upper respiratory infection.