Table 2. Univariate analysis and multivariate analysis of factors associated with level-II, and level-III/IV lymph node metastasis in the derivation group (n=460).

Variables	Level II								Level III–IV
	Univariate analysis				Multivariate analysis				Univariate analysis				Multivariate analysis
	(−), N=388	(+), N=72	P		OR	95% CI	P		(−), N=274	(+), N=186	P		OR	95% CI	P
Age			0.654								0.110
<55	326 (84.0)	62 (86.1)							225 (82.1)	163 (87.6)
≥55	62 (16.0)	10 (13.9)							49 (17.9)	23 (12.4)
Size, mm			<0.001				0.001				<0.001				0.001
<10	229 (59.0)	20 (27.8)			1				189 (69.0)	60 (32.3)			1
10–20	118 (30.4)	30 (41.7)			2.56	1.26–5.19			67 (24.5)	81 (43.5)			3.72	2.20–6.26
>20	41 (10.6)	22 (30.6)			5.15	2.19–12.11			18 (6.6)	45 (24.2)			5.85	2.76–12.37
Sex			0.276								0.181
Male	110 (28.4)	25 (34.7)							74 (27.0)	61 (32.8)
Female	278 (71.6)	47 (65.3)							200 (73.0)	125 (67.2)
Location			<0.001				0.001				<0.001				0.002
Upper	93 (24.0)	34 (47.2)			5.95	2.79–12.65			69 (25.2)	58 (31.2)			1.86	1.04–3.35
Middle	170 (43.8)	21 (29.2)			1				111 (40.5)	80 (43.0)			1
Lower	116 (29.9)	12 (16.7)			1.17	0.49–2.77			92 (33.6)	36 (19.4)			0.44	0.24–0.81
Whole	9 (2.3)	5 (6.9)			2.81	0.69–11.51			2 (0.7)	12 (6.5)			5.63	1.12–28.4
Left/right			0.619								0.150
Left	187 (48.2)	37 (51.4)							141 (51.5)	83 (44.6)
Right	201 (51.8)	35 (48.6)							133 (48.5)	103 (55.4)
Bilaterality	51 (13.1)	17 (23.6)	0.022		1.26	0.60–2.66	0.54		30 (10.9)	38 (20.4)	0.005		1.19	0.62–2.27	0.61
HT	70 (18.0)	11 (15.3)	0.572						47 (17.2)	34 (18.3)	0.756
Multifocality	143 (36.9)	22 (30.6)	0.306						92 (33.6)	73 (39.2)	0.213
ETE	78 (20.1)	23 (31.9)	0.026		1.14	0.58–2.25	0.711		43 (15.7)	58 (31.2)	<0.001		1.16	0.63–2.09	0.63
Prelaryngeal			<0.001				<0.001				<0.001				0.001
0	325 (83.8)	33 (45.8)			1				247 (90.1)	111 (59.7)			1
1–2	59 (15.2)	31 (43.1)			3.94	2.06–7.53			26 (9.5)	64 (34.4)			2.84	1.53–5.26
≥3	4 (1.0)	8 (11.1)			17.08	4.31–67.7			1 (0.4)	11 (5.9)			4.19	0.48–36.63
Pretracheal			<0.001				0.21				<0.001				0.001
0	227 (58.5)	24 (33.3)			1				189 (69.0)	62 (33.3)			1
1–2	117 (30.2)	23 (31.9)			1.60	0.77–3.33			71 (25.9)	69 (37.1)			2.28	1.33–3.91
≥3	44 (11.3)	25 (34.7)			2.12	0.89–5.10			14 (5.1)	55 (29.6)			6.01	2.70–13.42
Paratracheal			<0.001				0.003				<0.001				0.001
0	206 (53.1)	21 (29.2)			1				179 (65.3)	48 (25.8)			1
1–2	117 (30.2)	18 (25.0)			1.14	0.52–3.47			68 (24.8)	67 (36.0)			2.98	1.70–5.23
≥3	65 (16.8)	33 (45.8)			3.15	1.53–6.52			27 (9.9)	71 (38.2)			4.99	2.59–9.61

HT, hashimoto thyroiditis; ETE, extrathyroidal extension.