What it’s used for
The Neiman Imaging Comorbidity Index (NICI) is an easily calculated measure of comorbidity burden that specifically predicts future advanced imaging use (CT, MRI and PET). Researchers can use the NICI to risk-adjust patients in studies for which imaging use is an outcome.
Why it’s important
Existing risk indices and scores are effective in predicting various types of utilization of healthcare resources or adverse health outcomes (i.e., infection or death), but there was no scoring system specifically designed with imaging as an outcome variable. The NICI provides better discrimination in predicting the use of advanced imaging than the most frequently used risk adjustment score—the Charlson Comorbidity Index (CCI)—which was devised in a cancer population to predict mortality.
Development and Internal Validation
The NICI was built using claims data from a large single private payer. A numerical index was created in a development cohort (70% of the total dataset) using weights assigned to each comorbidity, based on regression coefficients. Internal validation of assigned scores was performed in the remaining 30% of claims, wherein the ability of the NICI to predict the use of advanced imaging was compared to that of the CCI.
External Validation
To assess the broader generalizability of the NICI to different insured populations and verify its superior performance compared to the CCI, the NICI was validated in three nationally representative populations including patients insured by Medicare (fee-for-service and Medicare Advantage), Medicaid, and multiple private payers.