OBJECTIVES: Data linkage is a valuable resource for observational studies. This study examines the added value of linked data over a single data source by comparing the 2011 Charlson Comorbidity Index (CCI) calculated using claims data only, electronic health records (EHRs) only, and linked claims-EHR among patients with asthma.

METHODS: The de-identified Oracle EHR Real-World (OERWD) data (extracted June 2023) was linked to a national US claims data source (2015-2022). Included were patients with an asthma diagnosis who had ≥1 EHR encounter, ≥1 claim, and ≥1 asthma treatment of montelukast as monotherapy or inhaled corticosteroids identified from claims. Descriptive analyses were performed and paired t-tests assessed group differences: (1) CCI derived from claims only (‘CCI-claims') versus CCI derived from linked claims-EHR (‘CCI Claims-EHR’) and (2) CCI derived from EHR only (‘CCI-EHR') vs CCI Claims-EHR.

RESULTS: Patients with asthma had a mean±standard deviation (SD) age of 28.78±20.50 years, were 59.36% female, 54.69% white, 21.36% black or African American, and 24.92% Hispanic or Latinx. Among the 109,076 patients with asthma, CCI-claims was 0.54±1.18 while the CCI-EHR was 0.39±0.81. CCI Claims-EHR was estimated at 0.89±1.37. Mean CCI values were 65% higher for CCI Claims-EHR compared to CCI-claims, and 128% higher compared to CCI-EHR (p<0.001 for all).

CONCLUSIONS: Comorbidity information derived from linked data adds significantly to the comorbidity information coming from claims or EHR alone and could present a more complete picture of the patient clinical profile.