Congestive heart failure in the United States - Is there more than meets the I(CD code)? The Corpus Christi Heart Project

Background: Congestive heart failure (CHF) is increasing as a public health problem in the United States. The ability to quantify this problem has bee n limited by a lack of data regarding the validity of CHF identification. Objective: To assess the validity of the use of International Classificatio n of Diseases, Ninth Revision, Clinical Modification (ICD) codes to identif y hospitalizations with clinical evidence of an episode of acute CHF in dat a of The Corpus Christi Heart Project, a population-based surveillance prog ram for hospitalized coronary heart disease. Methods: The validation standard was a composite variable including the pre sence of physician diagnosed acute CHF or radiographic evidence of pulmonar y edema. Data were abstracted from the medical records of 5083 patients ide ntified as hospitalized for possible acute myocardial infarction, aortocoro nary bypass surgery, percutaneous transluminal coronary angioplasty, and re lated revascularization procedures in the Corpus Christi Heart Project. Dis charge diagnoses, a secondary source of data, were used to apply 3 computer algorithms to assess the assignment of ICD codes. Results: The prevalence of clinically documented CHF was 27.1% (1376/5083). The ICD code 4;28 (CHF), assigned as the primary or a secondary discharge diagnosis, was associated with 62.8% sensitivity, 95.4% specificity, 83.5% positive predictive value, 87.4% negative predictive value, and a 24.8% und erenumeration of CHF-related hospitalizations. An algorithm based on a seri es of ICD codes was associated with 67.1% sensitivity, 92.6% specificity, 7 7.1% positive predictive value, 88.3% negative predictive value, and a 13.0 % underenumeration of CHF-related hospitalizations. Conclusions: Reliance on ICD codes results in the exclusion of one third of the patients with clinical evidence of acute CHF. This underenumeration is compounded by the typical reliance on the first listed diagnosis. Congesti ve heart failure may be a greater public health problem than currently reco gnized. The allocation of resources for relevant surveillance, research, me dical care, and preventive efforts should be reevaluated.