Table 2. Multivariable logistic regression and sensitivity analyses for SFR.

Model	OR (intelligent versus flexible)	95% CI	P value
A: unadjusted	1.91	1.02–3.68	0.047
B: + clinical variables	1.86	0.96–3.73	0.07
C: + stone complexity	1.74	0.87–3.60	0.13
D: + comorbidities (full)	1.72	0.83–3.68	0.15

Operative time is excluded from the primary models because it is a post-treatment variable (see Methods). The full model D is adjusted for age, sex, BMI, preoperative infection, stone size, stone CT value, stone multiplicity, stone location, hypertension, diabetes, and prior ureteral surgery. Cross-method comparison demonstrates consistent attenuation of the sheath effect. BMI, body mass index; CI, confidence interval; CT, computed tomography; OR, odds ratio; SFR, stone-free rate.