Table 5.

Comparison between base models and models with propensity score

ModelKey Variables Included/ExcludedLR χ2 (df)ComparisonDifference in LR χ2 (df )P > χ2Significant Key VariablesInference
1ACEI/ARB, diabetes, CHF, and hypertension184.4894 (df = 11)ACEI/ARB, diabetes, and CHF
2ACEI/ARB, diabetes, CHF, hypertension, and propensity score184.7427 (df = 12)2 versus 10.2533 (df = 1)0.61480ACEI/ARBPossible high collinearity between propensity score and diabetes, CHF, and hypertension because diabetes and CHF are significant in the base model. Addition of all four variables (diabetes, CHF, hypertension, and propensity score) adds no value to the model.
3ACEI/ARB and propensity score (excludes diabetes, CHF, and hypertension)180.9792 (df = 9)2 versus 33.7635 (df = 3)0.05238ACEI/ARB and propensity scoreConfirms high collinearity between propensity score and diabetes, CHF, and hypertension. Addition of diabetes, CHF, and hypertension adds no value to the model when propensity score is already present. Supports the notion that propensity score may be used as a proxy for a disease index for these diseases.
4Diabetes, CHF, hypertension, and propensity score (excludes ACEI/ARB)179.2128 (df = 11)2 versus 45.5299 (df = 1)0.01869NoneACEI/ARB has independent effect on AKI. Addition of ACEI/ARB significantly contributes to the model.
5Propensity score (excludes ACEI/ARB, diabetes, CHF, and baseline hypertension)175.4759 (df = 8)3 versus 55.5033 (df = 1)0.01898Propensity scoreACEI/ARB has independent effect on AKI. Addition of ACEI/ARB significantly contributes to the model.
4 versus 53.7369 (df = 3)0.05322Confirms high collinearity between propensity score and diabetes, CHF, and hypertension. Addition of diabetes, CHF, and baseline hypertension adds no value to the model when propensity score is already present. Supports the notion that propensity score may be used as a proxy for a disease index for these diseases.
6Diabetes, CHF, hypertension (excludes ACEI/ARB and propensity score)178.7873 (df = 10)1 versus 65.7021 (df = 1)Diabetes, CHF, and hypertensionACEI/ARB has independent effect on AKI.