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Technical Report 30: Risk Adjustment: Guide to the V21 and Nosos Risk Score Programs

Wagner TH, Stefos T, Moran E, Cashy J, Shen ML, Gehlert E, Asch SM, Almenoff P. Technical Report 30: Risk Adjustment: Guide to the V21 and Nosos Risk Score Programs. Menlo Park: HERC; 2016 Feb 3. 15 p. Report No.: 30.


This document provides directions for creating the Centers for Medicare and Medicaid (CMS) Hierarchical Condition Categories (HCC) version 21 (V21) risk scores and Nosos risk scores from the VA MedSAS and CDW data. (Note: Nosos is the Greek word for 'chronic disease'.) The science behind Nosos is documented the paper paper "Risk Adjustment Tools for Learning Health Care Systems: A Comparison of DxCG and CMS-HCC V21" (Wagner et al., 2016, Health Services Research; DOI: 10.1111/1475-6773.12454). The purpose of the Nosos program is to create risk scores for VA patients, so that researchers may adjust for risk when making comparisons of treatments or outcomes. The HCC risk scores primarily use the patients' diagnoses (ICD-9 codes), age and gender. The Nosos score builds on this, adding pharmacy records as well as VA-specific items such as VA priority status and VA-computed costs. The Nosos scores are computed by first computing the HCC risk scores using the V21 program. These risk scores, along with the additional factors, are then used as predictors in a regression model to model the annual VA cost for each patient. Estimates are then rescaled so that the mean Nosos score for the population will always equal one. In order to make it easier for researchers to customize the risk scores for their own purposes, we have attempted to present the scoring algorithm as a series of modular SAS macros, with minimal dependence between different tasks. For example, if a researcher wishes to use different diagnoses than what we have presented (such as excluding certain types of visits) it will only be necessary to modify the macro that extracts ICD-9 codes. A researcher who does not want to use pharmacy codes can skip the pharmacy extract macro and use a modified version of the regression macro that does not include pharmacy codes. See Appendix A for an example of pulling data and scoring Nosos for a complete fiscal year.

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