The National Hospital Care Survey Is a Unique Source of Data on Rare Diseases.

Objectives: This study aims to demonstrate the usefulness of the National Hospital Care Survey (NHCS) for studying rare diseases.

Methods: NHCS contains data on millions of hospital patients from participating US hospitals, including diagnoses coded using 10th revision of International Classification of Diseases, Clinical Modification, making it likely that some of the patients have a diagnosed rare disease. The data for 2016 are unweighted and are not nationally representative. The Orphanet Nomenclature Pack lists 877 10th revision of the International Classification of Diseases codes that correspond to 536 rare diseases. Using Orphanet Nomenclature Pack, we identified NHCS patients with diagnosed rare diseases. We demonstrate the usefulness of NHCS for studying rare diseases by reporting, for each rare disease, the number of patients in NHCS with the disease, the average number of hospital encounters per patient, the average length of hospital stay, and the percent of patients who died either in-hospital or within 90 days after discharge.

Results: In just 1 year of NHCS, we identified hundreds of rare diseases with ≥30 patients each (313 rare diseases in the inpatient setting and 273 in the emergency department setting). Although 10th revision of the International Classification of Diseases, Clinical Modification codes identify a small percent of known rare diseases, 12.9% of inpatient patients and 3.4% of emergency department patients had a diagnosed rare disease.

Conclusions: NHCS is a rich source of administrative and electronic health record data on hospital patients with rare diseases, providing unique variables and observations on many patients. Although the percent of patients with each rare disease is low, a large percent of hospital patients has a rare disease.