Positive predictive value of ICD-9-CM codes to detect acute exacerbation of COPD in the emergency department.

BACKGROUND: Accurate identification of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) visits by International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes will help organizations monitor quality of care for this common condition. A study was undertaken to validate ICD-9-CM coding for accurate identification of AECOPD visits.
METHODS: In a retrospective cohort study at two academic emergency departments (EDs) from July 2005 to June 2006, ICD-9-CM codes 491.2x (obstructive chronic bronchitis), 492.8 (other emphysema), and 496 (chronic airway obstruction, not elsewhere classified) in the principal diagnosis field were used to identify AECOPD visits. A random sample of 100 visits by patients age > or = 55 years of age was selected at each institution, and cases were confirmed by chart review consensus by two emergency physicians. The case definition for AECOPD was current respiratory infection, change in cough, or change in sputum in a patient with physician-diagnosed COPD.
RESULTS: On the basis of the selection criteria, 644 eligible visits were identified during the study period, and detailed chart review was performed for 200 randomly selected visits. Patients had a median age of 71 years, 50% were female, and 79% were white. Some 193 (97%) of the visits were confirmed to meet the case definition for AECOPD. Most cases were identified with the code 491.2x. All but one of the false positives were coded as 496, presumably because of lack of another billable diagnosis for these visits. DISCUSSION: In the first known chart validation of ICD-9-CM codes for identification of AECOPD visits, the proposed ICD-9-CM codes accurately identified cases of AECOPD in the ED. The study contributed to the use of these codes in the National Committee for Quality Assurance's new quality indicator for management of AECOPD.