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Editor's Correspondence
July 27, 1998

ACE Inhibitors, Congestive Heart Failure, and ICD-9-CM Codes

Arch Intern Med. 1998;158(14):1575-1576. doi:

In reply

We appreciate the opportunity afforded by Piwinski's letter to further describe our methods and to present updated 1995 and 1996 information on national patterns of ACE inhibitor use in congestive heart failure (CHF). Our conclusion remains unaltered and inescapable: ACE inhibitors are currently vastly underutilized in the treatment of CHF.

Piwinski discusses 2 issues related to the diagnostic coding of congestive heart failure in our analysis of the use of ACE inhibitors. We limited our analysis to visits from patients whose ICD-9-CM code1 included the specific term congestive heart failure. We used this approach because of the likely imprecision in diagnostic labels applied to outpatients with CHF and the predominant use of nonspecific diagnostic categories. Using this approach, we did not attempt to identify specific subtypes of CHF, nor did we attempt to infer a diagnosis of CHF from ICD-9-CM codes that might be suggestive but not necessarily indicative of irreversible CHF. Therefore, as Piwinski points out, we included patients diagnosed as having CHF secondary to hypertension (a subset of ICD-9-CM codes 402 and 404) and did not include patients who otherwise would be identified by the suggestive diagnoses of cardiomyopathy (code 425) and "ill-defined descriptions and complications of heart disease" (code 429, including myocarditis).