Table 3.

Effect modification analysis and predicted probability of N+.

	Adjusted OR	Model Estimates
	[95% CI]	Calculated Probability (95% PI), %	Observed Percentage, %
Tumor size <1 cm
Confined to the appendiceal wall	[Ref]	2.2 (0.1–3.8)	2.1
Confined to the appendiceal wall + LVI	10.1 [2.71–37.84]	18.1 (2.3–3.4)	16.7
Invading the subserosa and beyond	1.39 [0.50–3.88]	2.9 (0.1–5.1)	2.9
Invading the subserosa and beyond + LVI	14.1 [4.85–41.24]	23.4 (10.1–36.8)	24.3
≥1 cm but <2 cm
Confined to the appendiceal wall	[Ref]	13.9 (8.7–19.2)	14.6
Confined to the appendiceal wall + LVI	5.86 [2.69–12.79]	47.8 (32.2–63.3)	48.7
Invading the subserosa and beyond	0.73 [0.41–1.28]	10.6 (7.3–13.8)	10.8
Invading the subserosa and beyond + LVI	3.07 [1.74–5.42]	32.7 (25.2–40.3)	33.8
≥2 cm
Confined to the appendiceal wall	[Ref]	30.1 (22.6–37.5)	31.7
Confined to the appendiceal wall + LVI	3.85 [2.01–7.36]	61.5 (49.1–73.9)	64.4
Invading the subserosa and beyond	1.54 [0.86–2.76]	39.6 (28.9–50.3)	41.1
Invading the subserosa and beyond + LVI	5.20 [2.58–10.50]	68.2 (55.4–81.1)	73.2

All patients were included in the model (n = 5353). This model was created using the same predictors as the ones included in Table 2 plus a two- and three-way term interaction between tumor size, tumor depth, and lymphovascular invasion; the coefficients for this model are presented in Table S3.