Table 4. Univariate and multivariate linear correlation analysis between surgery (dependence variable) and independence variables such as: age, gender, blood cultures, previous endocarditis, native valve, complications, WBC/RBC score, CPR at T0 and HIV+.

* = significant test; R = Pearson’s linear correlation coefficient; R_partial = the partial correlation coefficient is the coefficient of correlation of the variable with the dependent variable, adjusted for the effect of the other variables in the mode; WBC = white blood cells; RBC = red blood cells; CRP = C-reactive protein (normal values < 5 mg/dl); T0 = within first week of admission; HIV: human immunodeficiency virus

Linear correlation analysis	Univariate analysis R (p-value)	Multivariate analysis (Rpartial; p-value)
		Multiple linear correlation coefficient = 0.797
Surgery / Age	-0.106 (0.438)	Rpartial = -0.392; p-value = 0.0071 *
Surgery / Gender	-0.603 (<0.0001) *	Rpartial = 0.126.; p-value = 0.405
Surgery / Blood Cultures	-0.225 (0.096)	Rpartial = 0.022; p-value = 0. 887
Surgery / Previous endocarditis	0.056 (0.684)	R partial = -0.128; p-value = 0.396
Surgery / Native valve	-0.142 (0.307)	Rpartial = 0.053; p-value = 0.726
Surgery / Complications	0.603 (< 0.0001) *	Rpartial = 0.339; p-value = 0.0212 *
Surgery / CPR at T0	0.642 (< 0.0001) *	Rpartial = -0.031; p-value = 0.840
Surgery / WBC/RBC score	0.213 (0.116)	Rpartial = 0.071; p-value = 0.638
Surgery / HIV infected	-0.616 (< 0.0001) *	Rpartial = -0.336; p-value = 0.0223 *