Table 5.

Comparison between base models and models with propensity score

Model	Key Variables Included/Excluded	LR χ² (df)	Comparison	Difference in LR χ² (df )	P > χ²	Significant Key Variables	Inference
1	ACEI/ARB, diabetes, CHF, and hypertension	184.4894 (df = 11)	–	–	–	ACEI/ARB, diabetes, and CHF	–
2	ACEI/ARB, diabetes, CHF, hypertension, and propensity score	184.7427 (df = 12)	2 versus 1	0.2533 (df = 1)	0.61480	ACEI/ARB	Possible 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.
3	ACEI/ARB and propensity score (excludes diabetes, CHF, and hypertension)	180.9792 (df = 9)	2 versus 3	3.7635 (df = 3)	0.05238	ACEI/ARB and propensity score	Confirms 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.
4	Diabetes, CHF, hypertension, and propensity score (excludes ACEI/ARB)	179.2128 (df = 11)	2 versus 4	5.5299 (df = 1)	0.01869	None	ACEI/ARB has independent effect on AKI. Addition of ACEI/ARB significantly contributes to the model.
5	Propensity score (excludes ACEI/ARB, diabetes, CHF, and baseline hypertension)	175.4759 (df = 8)	3 versus 5	5.5033 (df = 1)	0.01898	Propensity score	ACEI/ARB has independent effect on AKI. Addition of ACEI/ARB significantly contributes to the model.
			4 versus 5	3.7369 (df = 3)	0.05322		Confirms 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.
6	Diabetes, CHF, hypertension (excludes ACEI/ARB and propensity score)	178.7873 (df = 10)	1 versus 6	5.7021 (df = 1)		Diabetes, CHF, and hypertension	ACEI/ARB has independent effect on AKI.