Table S2.

Definitions of COPD exacerbations by severity

Type of COPD exacerbations	Definition
Mild COPD exacerbation	An ED visit OR office visit OR outpatient non-ED visit with: 1) any of the diagnosis codes indicative of an acute exacerbation in the primary position AND a secondary ICD-9-CM code for COPD; OR 2) a COPD diagnosis code in the primary position; OR 3) a diagnosis for respiratory failure in the primary position AND a secondary ICD-9-CM code for COPD (no hospitalization); AND 4) a pharmacy claim for any of the antibiotics commonly used for respiratory infections within seven days of the visit; OR 5) a prescription claim for an oral corticosteroid within seven days of the visit
Moderate COPD exacerbation	A hospitalization with: 1) a secondary ICD-9-CM code for COPD AND any of the diagnosis codes indicative of an acute exacerbation in the primary position; OR 2) a COPD diagnosis code in the primary position; AND 3) no respiratory failure
Severe COPD exacerbation	1) A hospitalization with any of the diagnosis codes indicative of an acute exacerbation in the primary position; AND a secondary ICD-9-CM code for COPD AND a secondary ICD-9-CM code for respiratory failure; OR 2) a hospitalization with a COPD diagnosis code in the primary position AND a secondary ICD-9-CM code for respiratory failure; OR 3) a hospitalization with a principal diagnosis for respiratory failure AND a secondary ICD-9-CM code for COPD

Abbreviations: ED, emergency department; ICD-9-CM, International Classification of Diseases – Ninth Revision – Clinical Modification.