Hypertrophic cardiomyopathy (HC) is the most common genetic heart disease and an important cause of sudden death and heart failure symptoms. The current prevalence for HC (1:500) is based on echocardiographic population studies in which a substantial proportion of affected subjects have not come to clinical recognition. Therefore, we sought to define the subset of patients with HC who are diagnosed in the US. A proprietary integrated claims database including medical condition International Classification of Diseases, Ninth Revision diagnostic codes for over 160 million individual patients in the US was interrogated for 2013 to identify the prevalence of clinically recognized HC. Patients with ≥1 claim for any of the HC International Classification of Diseases, Ninth Revision diagnosis codes from January to December 2013 were identified. The combined occurrence rate of HC was stratified by age and gender and multiplied by the 2013 United States population in the same age/gender categories to produce the final projected prevalence. The analysis was performed on 169,089,614 patients, of whom 59,009 unique patients were identified with ≥1 claim for HC. The projected estimated occurrence of diagnosed HC in the US in 2013 was 1:3,195 for a total of 98,958 subjects. Average age at HC diagnosis was in the fifth decade of life, with 43% of the cohort composed of women. In conclusion, leveraging a claims-based data analytic technique, about 100,000 patients are diagnosed clinically with HC in the US, an occurrence which is less than the prevalence reported in systematic population studies based on echocardiographic diagnosis. This observation supports the view that many patients with HC are undiagnosed throughout life and enhances our understanding of the burden of this genetic heart disease on the health care system.
Hypertrophic cardiomyopathy (HC) is a common genetically inherited heart disease and represents an important cause of cardiovascular morbidity and mortality in patients of all ages. The prevalence of HC in the general population has been estimated at 1:500, based on numerous epidemiologic studies in the United States (US) and globally, in which unrelated subjects were randomly selected from the general population to undergo echocardiographic evaluation. However, these estimated figures largely represent clinically unrecognized disease in the general population because most patients in these studies were not known to be affected. In addition, most patients with HC never develop (or recognize) cardiovascular symptoms, experience an adverse disease-related event or are identified with another clinical marker (e.g., abnormal electrocardiogram and family history) which could lead to clinical recognition. Thus, we sought to define the subset of patients with HC who are clinically diagnosed (and treated) in the US, with important implications to our understanding of the burden of this disease on the health care system.
Methods
We queried a large proprietary integrated claims database (Symphony Health Solutions [SHS], Phoenix, Arizona), which includes medical condition diagnostic codes ( International Classification of Diseases, Ninth Revision [ICD-9]) for over 160 million individual patients (>1/2 census population of 316,159,818 in 2013 ) in the United States. These claims are captured in each of the US states and include all insurance types, including Medicare and Medicaid. The database is composed of electronically submitted private practitioner (Centers for Medicare and Medicaid Services 1500) claims and hospital and facility (uniform bill 04) claims within a given year. The private practitioner claims include diagnostic, therapeutic, and procedure information from over 860,000 practitioners of all medical and surgical specialties, and practices of all sizes. The institutional claims encompass diagnostic, therapeutic, and procedure information, including administered medications, from hospitals and clinics and are inclusive of inpatient and outpatient encounters, including emergency department care.
To identify patients with diagnosed HC, subjects with ≥1 claim for the ICD-9 diagnosis codes for HC (i.e., 425.1, 425.11, 425.18) from January 1, 2013 to December 31, 2013 were searched. To avoid double counting of individual patients, patient-level records from each data source were linked longitudinally across settings of care through a Health Insurance Portability and Accountability Act-compliant, deidentified unique patient identifier that matched patients using a hash generated from the patient’s first name, last name, gender, and date of birth. Because HC is a lifelong condition, period prevalence, which reflects both the incidence and duration of disease, was selected as the most appropriate measure of disease frequency in this analysis. In light of recently published clinical guidelines for HC recommending annual surveillance visits, the period prevalence was defined as the number of individual patients with HC identified during 2013 divided by the total United States population alive at the end of this year (reported as cases per 100,000 subjects). Crude prevalence of HC was then stratified by dividing the number of patients with ≥1 HC claim in each age and gender category by the total number of patients in that stratum and then multiplied by the 2013 United States population to produce the final projected estimated prevalence of diagnosed HC.
Results
Over the study period, 169,089,614 unique patients were identified, of which 59,009 had ≥1 HC diagnostic claim ( Figure 1 ). The final occurrence of diagnosed HC in the United States for 2013 was estimated to be 1:3,195. This prevalence estimate yielded a total of 98,958 patients with HC, approximately half of whom are presumed to be symptomatic based on previous large HC cohort studies. The average age of HC diagnosis was in the fifth decade of life, with 43% of the HC cohort comprised women. There were no age differences seen across the 3 diagnostic codes, which appeared to be internally consistent ( Figure 2 ).
