Table 4.

Threshold effect analysis of systemic immune-inflammation index and serum ferritin stratified by gender.

Gender	Male	Female
Model 1, β (95% CI)
Linear effect model	−0.06 (−0.10, −0.03) <0.0001	−0.01 (−0.02, −0.00) 0.0465
Model 2, β (95% CI)
Inflection point (K)	399	615
< K	−0.11 (−0.21, −0.00) 0.0430	−0.04 (−0.06, −0.02) 0.0001
> K	−0.05 (−0.09, −0.01) 0.0083	0.01 (−0.00, 0.03) 0.1213
LLR	0.396	0.001

Model 1: Linear effects model; Model 2: Non-linear effects model.

In the subgroup analysis stratified by each covariate, the model is not adjusted for the stratification variable itself.