Identifying Older Adults with Serious Illness: Transitioning from ICD-9 to ICD-10.

CONTEXT: Identifying the seriously ill population is integral to improving the value of health care. Efforts to identify this population using existing data are anchored to a list of severe medical conditions (SMCs) using diagnostic codes. Published approaches have utilized International Classification of Diseases, Ninth Revision (ICD-9) codes, which has since been replaced by ICD-10.

OBJECTIVES: We translated SMCs from ICD-9 to ICD-10 using a refined code list. We aimed to test the hypothesis that people identified by ICD-9 or ICD-10 codes would have similar Medicare costs, healthcare utilization, and mortality.

METHODS: Using data from the National Health and Aging Trends Study linked to Medicare claims, we compared samples from periods using ICD-9 (2014) and ICD-10 (2016). We included participants with 6-months of fee-for-service Medicare data before their interview date who had a SMC identified within that period. We compared the groups' demographic, functional, and medical characteristics, and followed them for six months to compare outcomes.

RESULTS: Among subjects in the 2016 (ICD-10) sample, 19.9% were hospitalized, 24.6% used the emergency department, 7.2% died, and average Medicare spending totaled $9,902.04 over six months of follow-up. We observed no significant differences between the 2014 and 2016 samples (p>0.05); both samples represent 18% of Medicare fee-for-service beneficiaries.

CONCLUSION: Identifying the seriously ill population using currently available data requires using ICD-10 to define SMCs. Routine measurement of function, quality of life and caregiver strain will further enhance the identification process and efficiently target palliative care services and appropriate quality measures.