Use of and Comorbidities Associated With Diagnostic Codes for COVID-19 in US Health Insurance Claims.

Accurate identification of COVID-19 diagnosis in patient medical records is essential for studies using administrative data to examine morbidity, mortality, and risk factors associated with COVID-19.1 Before April 1, 2020, the Centers for Disease Control and Prevention suggested using the existing International Statistical Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code B97.29 (other coronavirus as the cause of diseases classified elsewhere) as the primary diagnostic code for patients infected with COVID-19.2 On April 1, 2020, a new code U07.1 (2019-nCoV acute respiratory disease) was added to ICD-10-CM3 and was rapidly adopted by hospitals.4 Our study examined how nonhospital and hospital health care professionals have used these diagnostic codes in practice using a national medical claims data set in the US. We analyzed the comorbidities associated with COVID-19 diagnosis to assess the specificity of the legacy code and the importance of using both codes.