Table 3 Threshold effect analysis of E₂ level (100pg/mL) in cycles with lower E₂ level (< 1400 pg/mL)

Model I (linear)

OR

95% CI

p value

Linear effect

0.970

(0.950, 0.990)

0.004

Model II (polyline)

OR

95% CI

p value

Predicted threshold (K, E ₂ level, 100pg/mL)

3

Effect 1 (< K)

1.074

(1.000, 1.153)

0.051

Effect 2 (> K)

0.944

(0.919, 0.970)

< 0.001

variability of effectiveness

0.572

(0.499, 0.646)

Logarithmic likelihood ratio test

0.004