Nomogram to predict the risk of endoscopic removal failure with forceps/baskets for treating submandibular stones

Table 1 Clinical features of the enrolled stones

Variables
Sex
Male	99 (46.9%)
Female	112 (53.1%)
Age of the patient
< 44 yr	123 (58.3%)
≥ 44 yr	88 (41.7%)
Intraductal stone treatment history
Yes	34 (16.1%)
No	177 (83.9%)
Involved side
Left	100 (47.4%)
Right	111 (52.6%)
Amounts of stones
Single	180 (85.3%)
Multiple	31 (14.7%)
Palpation
Positive	134 (63.6%)
Negative	77 (36.4%)
Location/cm
Range	0.42-5.69
Mean	3.48 ± 1.51
TD/mm
Range	1.23-12.00
Mean	5.17 ± 2.01
LD/mm
Range	0.57-9.26
Mean	4.97 ± 1.48
Surgical methods
Endoscopic removal	89 (42.2%)
ERF	122 (57.8%)

TD: Transverse diameter; LD: Longitudinal diameter; ERF: Endoscopic removal failure.

Table 2 Cutoff values for the location, transverse and longitudinal diameter of the enrolled stones

Variables	Cutoff	Youden’s index	Sensitivity	Specificity
Location/cm	3.76	0.581	0.719	0.862
TD/mm	4.97	0.675	0.787	0.877
LD/mm	5.14	0.638	0.730	0.908

TD: Transverse diameter; LD: Longitudinal diameter; ERF: Endoscopic removal failure.

Table 3 Results of Pearson’s chi-square test

Variables		Endoscopic removal	ERF	χ2	P value
Sex	Male	42	57	0.005	0.946
	Female	47	65
Age of the patient	< 44	54	69	0.359	0.549
	≥ 44	35	53
Intraductal stone treatment history	Yes	12	22	0.788	0.244
	No	77	100
Involved side	Left	43	57	0.052	0.819
	Right	46	65
Amounts of stones	Single	74	106	0.005	0.945
	Multiple	15	16
Palpation	Positive	38	96	28.764	< 0.001a
	Negative	51	26
Location	< 3.76 cm	75	38	58.382	< 0.001a
	≥ 3.76 cm	14	84
TD	< 4.97 mm	76	28	80.274	< 0.001a
	≥ 4.97 mm	13	94
LD	< 5.14 mm	82	32	34.586	< 0.001a
	≥ 5.14 mm	7	90

^aP < 0.05. ERF: Endoscopic removal failure; TD: Transverse diameter; LD: Longitudinal diameter; CI: Confidence interval.

Table 4 Results of univariate and multivariate logistic regression analyses

Variables	Univariate			Multivariate
	Odds ratio	95%CI	P value	Odds ratio	95%CI	P value
Sex	1.288	0.745-2.228	0.366	-	-	-
Age of the patient	1.185	0.680-2.066	0.549	-	-	-
Intraductal stone treatment history	1.412	0.658-3.029	0.376	-	-	-
Involved side	1.066	0.617-1.842	0.819	-	-	-
Amounts of stones	1.026	0.496-2.123	0.945	-	-	-
Palpation	4.955	2.710-9.061	< 0.001a	-	-	-
Location/cm	11.842	5.956-23.547	< 0.001a	8.796	3.672-22.661	0.040a
TD/mm	19.626	9.516-40.481	< 0.001a	10.287	3.301-35.269	< 0.001a
LD/mm	32.946	13.791-78.106	< 0.001a	4.412	1.256-15.575	< 0.001a

^aP < 0.05. TD: Transverse diameter; LD: Longitudinal diameter; CI: Confidence interval.