Adapting the Rx-Risk-V for mortality prediction in outpatient populations.
OBJECTIVE
We sought to operationalize, test, and validate an outpatient pharmacy-based case-mix adjuster.


METHODS
Outpatients from the Department of Veterans Affairs (VA) prescribed a nonsteroidal anti-inflammatory drug (NSAID) or cyclooxygenase-2 selective drug during 2002 were identified. We updated and extended the Rx-Risk-V by adding 26 additional disease categories and mapping them to VA drug-class codes; derived empirical weights for each from a logistic model of 1-year mortality; adjusted for age, race and sex; and scored the weights into 1 measure of comorbidity. We compared the weighted score to the Deyo diagnosis-based comorbidity index and validated it in a national cohort of 260,321 outpatients with chronic heart failure (CHF).


RESULTS
One-year mortality among the 724,270-outpatient NSAID cohort was 1.6% (n = 11,766). Using a baseline model of age, race, and gender (c-index = 0.716), we found that the Deyo measure improved the prediction of mortality (c-index = 0.765), and the pharmacy comorbidity score further improved the prediction (c-index = 0.782), an increase of 25.8%. Using both, we found further improvement (c-index = 0.792). Among the CHF cohort, 9.7% (n = 25,251) died within 1 year. Performance of the baseline model controlling for age, race, and gender (c index = 0.620) improved with addition of the pharmacy comorbidity score (c index = 0.689), compared with the addition of the Deyo measure (c index = 0.651), an increase of 55.1%. Together, they slightly improved prediction in CHF patients (c index = 0.695).


CONCLUSIONS
The updated and extended Rx-Risk-V is useful for case-mix adjustment of mortality in an outpatient population.
Johnson
Michael L
ML
Houston Center for Quality of Care and Utilization Studies, Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030, USA. mjohnson@bcm.tmc.edu
El-Serag
Hashem B
HB
Tran
Tung Thomas
TT
Hartman
Christine
C
Richardson
Peter
P
Abraham
Neena S
NS
D000368:Aged; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use*; D015331:Cohort Studies; D052246:Cyclooxygenase 2 Inhibitors / Q000627:therapeutic use; D005260:Female; D006333:Heart Failure / Q000188:drug therapy / Q000401:mortality*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D020379:Risk Adjustment / Q000379:methods*; D018570:Risk Assessment; D014728:Veterans
D000894:Anti-Inflammatory Agents, Non-Steroidal; D052246:Cyclooxygenase 2 Inhibitors