Critique of the Week : A Chronic Disease Score with Empirically Derived Weights.

1. Critique of the Week: A Chronic Disease Score with Empirically Derived Weights. Daniel Clark, Michael Von Kroff, Kathleen Saunders, William Baluch and Gregory Simon.

2. Critique of the Week • Objective: • To develop a Chronic Disease Score with Empirically Derived Weights • To compare the Revised Chronic Disease Score (empirically derived weights) with Original (physician assigned weights) CDS and ADGs • To assess associations between the Predicted Costs, Utilization, Hospitalization and Death with total costs, outpatient cost, primary visits.

3. Critique of the Week • Significance: • To develop a reliable and more predictive Risk Adjuster for determining Capitation payments. • A wider range of medications are covered compared to the original CDS. • To asses the correlation between both the CDS and ADG to each of the outcome variable (predicted costs, utilization, hospitalization and death)

4. Critique of the Week • Hypotheses: • Not explicitly Conveyed • Probable Hypotheses; • The Revised CDS explains more variance in Predicted Costs, Utilization, Hospitalization and Death than the Original CDS and the ADGs. • The Revised CDS predicts the Costs, Utilization, Hospitalization and Death, to a higher degree than the Original CDS and the ADGs.

5. Critique of the Week • Data Collection: • Group Health Cooperation of Puget Sound in Western Washington State. • Adults (18 yrs or older). • Enrolled continuously at GHC for last six months of 1992. • 245,694 subjects were selected for the study.

6. Critique of the Week • Results: • Proxy measures for Disease severity (CDS & ADGs) considerably improve prediction of health care utilization and costs. • Both the Revised CDS and ADGs were equal in predicting primary visits and costs. • Revised CDS was best in prediction mortality.

7. Critique of the Week • Results

8. Critique of the Week • Results: • Variance explained in concurrent models was higher then the Variance explained for the Prospective period. • There was no clear better predictor (CDSs or ADGs) for the outcome variables.

9. Critique of the Week • Results

10. Critique of the Week • Results • For Concurrent Model; • No improvement over the revised CDS was found for total cost. • There was only marginal improvement in variance explained with the incorporation of ADGs and the original CDS into the same model.

11. Critique of the Week • Results • For the Prospective Model; • Improved prediction was achieved by the revised CDS relative to the original CDS • ADGs performed better on all outcomes in the concurrent model but the revised CDS performed slightly better in explained variance in total and outpatient costs

12. Critique of the Week • Results • Odds Ratio for Death and Hospitalization were estimated from predicted costs and Utilization. • The Revised CDS had stronger correlation with death than ADGs, Original CDS had the weakest correlation.

13. Critique of the Week Results Odds Ratio. • The odds ratio is a way of comparing whether the probability of a certain event is the same for two groups. • An odds ratio of 1 implies that the event is equally likely in both groups. • An odds ratio greater than one implies that the event is more likely in the first group. • An odds ratio less than one implies that the event is less likely in the first group.

14. Critique of the Week • Level of Study: Exploratory and Descriptive • Time Frame: Ex post facto (retrospective)

15. Critique of the Week • Operational definitions: • Not clearly given. • Assumed knowledge of various standardized Disease Severity Scores (CDSs, ADGs…etc). • Methods used were well documented and were adequate for reproducibility.

16. Critique of the Week • Methods: • A Revised CDS was created using Regression model using medication usage and age and gender, for a random half of the population. • Parameters associated with each medication variable were estimated for each of three outcomes: outpatient cost, primary care visits and total costs.

17. Critique of the Week • Methods: • These weights were then used to calculate a predicted score for total cost, Outpatient cost and primary care visits for the other half of the population. • The weights were also used to predict the outcome parameters for a Prospective Cohort. • The Predicted parameters were then correlated with the actual parameters. Also the Scores were correlated with risk of Hospitalization and Death.

18. Critique of the Week • Controls • Randomization • Testing the Regression model Scores on both Concurrent and Prospective gorups.

19. Critique of the Week • Identified Sources of Bias. • Revised CDS obtained from six months data compared to twelve data for Original CDS. • Not all enrollees had medications filled in the six month period. • Manipulation. • Endogeneity.

20. Critique of the Week • Generalizability: That particular Health Maintenance Organization (HMO). • Future Study: Testing and Validating the Revised CDS at different sites than the one used here.

21. Critique of the Week • Weak Research Methodology • Typical of a Pharmacoeconomic Study • Strong yet Simple statistical methods • Least Square Regression • Odds Ratio