Table 1.

Exacerbation definition by severity type

Exacerbation severity	Definition
Level I exacerbation (ambulatory)	A medical claim for an ER or outpatient visit with the following:
	1. COPD diagnosis code (ICD-9-CM code 491.xx, 492.xx, or 496.xx) in the primary position OR
	2. Respiratory failure diagnosis code (ICD-9-CM code 518.81, 518.83, or 518.84) in the primary position accompanied by a COPD diagnosis code in the secondary position OR
	3. Any diagnosis code indicative of an acute exacerbation (ICD-9-CM codes 466–466.19, 480–486, 487.0, 490, 493.12, 493.22, 493.92, 494.1, 506.0–506.3, 511.0–511.1, or 518.82) in the primary position and a COPD diagnosis code in the secondary position
	AND
	1. A prescription claim for any of the antibiotics commonly used for respiratory infections within 7 days of the visit OR
	2. A prescription claim for an oral corticosteroid within 7 days of the visit
Level II exacerbation (requiring hospitalization)	A medical claim for a hospitalization with the following:
	1. COPD diagnosis code in the primary position OR
	2. Any diagnosis code indicative of an acute exacerbation in the primary position and a COPD diagnosis code in the secondary position
	AND
	1. No respiratory failure diagnosis code in secondary position
Level III exacerbation (leading to acute respiratory failure)	A medical claim for a hospitalization with the following:
	1. COPD diagnosis code in the primary position and a respiratory failure diagnosis code in secondary position OR
	2. Any diagnosis code indicative of an acute exacerbation in the primary position and a COPD and a respiratory failure diagnosis code in the secondary position OR
	3. Respiratory failure diagnosis code in the primary position accompanied by a COPD diagnosis code in the secondary position

Abbreviations: ER, emergency room; ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification.