Interobserver and intraobserver reliability of skull base angles measured on magnetic resonance images

Table 1 Demographic data of the patients analyzed in the study

Characteristics	n
Sex
Total, n = 391
Females	247 (63.2)
Males	144 (36.8)
Age
Mean	45.26
Standard deviation	16.72
Minimum	18
Maximum	96
Age groups
18 and 19	18
20-29	63
30-39	72
40-49	77
50-59	71
60-69	60
70-79	21
80-89	8
90-99	1

Data are presented as n (%) or n.

Table 2 Results of the intraclass correlation coefficient analyses

Parameter	Subparameter	95 %CI		Intraclass correlation coefficient
		Lower bound	Upper bound
Reviewer 1	SBA	0.998	0.999	0.998
	mSBA	0.999	0.999	0.999
Reviewer 2	SBA	0.997	0.998	0.997
	mSBA	0.999	0.999	0.999
R1 vs R2 for M1	SBA	0.997	0.998	0.998
	mSBA	0.998	0.999	0.998
R1 vs R2 for M2	SBA	0.996	0.997	0.996
	mSBA	0.999	0.999	0.999

CI: Confidence interval; M1: First measurements; M2: Second measurements; mSBA: Modified skull base angle; R1: Reviewer 1; R2: Reviewer 2; SBA: Skull base angle.

Table 3 Comparison of the measured skull base angles between females and males

Interpretations by the reviewers	Female	Male	P value
SBA
R1	132.19 ± 4.88	130.92 ± 4.52	0.011
R2	132.22 ± 4.88	130.96 ± 4.49	0.012
mSBA
R1	118.23 ± 3.72	116.20 ± 3.66	< 0.001
R2	118.19 ± 3.70	116.20 ± 3.63	< 0.001

Data are presented as mean ± standard deviation. mSBA: Modified skull base angle; R1: Reviewer 1; R2: Reviewer 2; SBA: Skull base angle.

Table 4 Correlation between skull base angle measurements and age

Measurement and reviewer	Correlation coefficient	P value
SBA measurement by R1	0.014	0.788
SBA measurement by R2	0.021	0.685
mSBA measurement by R1	-0.235	< 0.001
mSBA measurement by R2	-0.233	< 0.001

mSBA: Modified skull base angle; R1: Reviewer 1; R2: Reviewer 2; SBA: Skull base angle.