Influence of Nomenclature in the Interpretation of Lumbar Disk Contour on MR Imaging: A Comparison of the Agreement Using the Combined Task Force and the Nordic Nomenclatures

E. Arana; F.M. Kovacs; A. Royuela; A. Estremera; H. Sarasíbar; G. Amengual; I. Galarraga; C. Martínez; A. Muriel; V. Abraira; J. Zamora; C. Campillo

doi:10.3174/ajnr.A2448

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Table 1:

Radiologic findings per vertebral level

Variable	L1-L2	L2-L3	L3-L4	L4-L5	L5-S1
CTF nomenclature
Intravertebral herniation (yes)^a	64 (24.2)	60 (22.6)	58 (21.9)	53 (20.0)	56 (21.1)
Disk contour^a
Normal	225 (84.9)	183 (69.1)	137 (51.7)	64 (24.2)	112 (42.3)
Bulging (>50%)	30 (11.3)	67 (25.3)	108 (40.8)	136 (51.3)	72 (27.2)
Protrusion focal (<25%)	8 (3.0)	6 (2.3)	16 (6.0)	53 (20.0)	47 (17.7)
Protrusion broad-based (25%–50%)	2 (0.8)	5 (1.9)	4 (1.5)	5 (1.9)	22 (8.3)
Extrusion	0 (0.0)	4 (1.5)	0 (0.0)	7 (2.6)	12 (4.5)
Nordic nomenclature
Intravertebral herniation (yes)^a	50 (18.9)	46 (17.4)	52 (19.6)	36 (13.6)	24 (9.1)
Disk contour^a
Normal	217 (81.9)	204 (77.0)	160 (60.4)	84 (31.7)	104 (39.2)
Bulging	45 (17.0)	46 (17.4)	97 (36.6)	137 (51.7)	98 (37.0)
Protrusion	3 (1.1)	11 (4.2)	8 (3.0)	39 (14.7)	60 (22.6)
Extrusion	0 (0.0)	4 (1.5)	0 (0.0)	5 (1.9)	3 (1.1)

a No. (%). All of the percentages are calculated over a total of 265 images (53 images seen by the 5 radiologists).

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Table 2:

Intraobserver agreement

Variable	Intraobserver Agreement CTF^a	Intraobserver Agreement Nordic^a
Intravertebral herniation	0.682 (0.389; 0.835)	0.694 (0.530; 0.852)
Disk contour at L1-L2, L2-L3, and L3-L4^b	0.750 (0.654; 0.824)	0.714 (0.608; 0.776)
Disk contour at L4-L5 and L5-S1
Considering bulging as abnormal^b	0.728 (0.622; 0.864)	0.642 (0.558; 0.816)
Considering bulging as normal^c	0.624 (0.538; 0.667)	0.565 (0.460; 0.717)

a Mean (5th percentile, 95th percentile) of κ values. Agreement is classified as almost perfect (κ value > 0.81), substantial (0.61–0.80), moderate (0.41–0.60), fair (0.21–0.40), slight (0.00–0.20), or poor (<0.00).
b Agreement in classifying images in the 2 following categories: normal vs bulging + focal protrusion + broad-based protrusion + extrusion, according to the CTF nomenclature; or normal vs symmetric bulging + protrusion (focal or broad-based) + hernia (extrusion or sequestration), according to the Nordic nomenclature.
c Agreement in classifying images in the 2 following categories: normal + bulging vs focal protrusion + broad-based protrusion + extrusion, according to the CTF nomenclature; or normal + symmetric bulging vs protrusion (focal or broad-based) + hernia (extrusion or sequestration), according to the Nordic nomenclature.

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Table 3:

Number of images classified by each radiologist as normal or abnormal using both nomenclatures and depending on whether bulging was considered to be normal or abnormal (levels L4-L5 and L5-S1)

	CTF								Nordic
	Control 1				Control 2				Control 1				Control 2
	Considering Bulging Abnormal^a		Considering Bulging Normal^b		Considering Bulging Abnormal^a		Considering Bulging Normal^b		Considering Bulging Abnormal^a		Considering Bulging Normal^b		Considering Bulging Abnormal^a		Considering Bulging Normal^b
	N	A	N	A	N	A	N	A	N	A	N	A	N	A	N	A
L4-L5
Rx1	5	48	32	21	2	51	30	23	11	42	32	21	13	40	32	21
Rx2	5	48	48	5	3	50	43	10	9	44	49	4	9	44	49	4
Rx3	13	40	37	16	14	39	43	10	21	32	42	11	25	28	39	14
Rx4	23	30	47	6	19	34	44	9	21	32	48	5	29	24	46	7
Rx5	18	35	36	17	22	31	36	17	22	31	50	3	23	30	52	1
L5-S1
Rx1	24	29	34	19	20	33	33	20	21	32	29	24	23	30	34	19
Rx2	16	37	42	11	11	42	46	7	11	42	49	4	18	35	50	3
Rx3	20	33	30	23	22	31	39	14	20	33	37	16	25	28	33	20
Rx4	28	25	44	9	24	29	40	13	28	25	43	10	35	18	44	9
Rx5	24	29	34	19	25	28	33	20	24	29	44	9	26	27	48	5

a Agreement in classifying images in the 2 following categories: normal vs bulging + focal protrusion + broad-based protrusion + extrusion, according to the CTF nomenclature; or normal vs symmetric bulging + protrusion (focal or broad-based) + hernia (extrusion or sequestration), according to the Nordic nomenclature.
b Agreement in classifying images in the 2 following categories: normal + bulging vs focal protrusion + broad-based protrusion + extrusion, according to the CTF nomenclature; or normal + symmetric bulging vs protrusion (focal or broad-based) + hernia (extrusion or sequestration), according to the Nordic nomenclature.

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Table 4:

Interobserver agreement

Variable	Interobserver Agreement CTF^a	Interobserver Agreement Nordic^a
Intravertebral herniation	0.530 (0.415; 0.657)	0.481 (0.236; 0.673)
Disk contour at L1-L2, L2-L3, and L3-L4^b	0.476 (0.398; 0.573)	0.473 (0.286; 0.560)
Disk contour at L4-L5 and L5-S1
Considering bulging as abnormal^b	0.562 (0.426; 0.788)	0.456 (0.179; 0.650)
Considering bulging as normal^c	0.407 (0.261; 0.597)	0.277 (0.000; 0.571)

a Mean (5th percentile, 95th percentile) of κ values. Agreement is classified as almost perfect (κ value > 0.81), substantial (0.61–0.80), moderate (0.41–0.60), fair (0.21–0.40), slight (0.00–0.20), or poor (<0.00).¹⁸
b Agreement in classifying images in the 2 following categories: normal vs bulging + focal protrusion + broad-based protrusion + extrusion, according to the CTF nomenclature; or normal vs symmetric bulging + protrusion (focal or broad-based) + hernia (extrusion or sequestration), according to the Nordic nomenclature.
c Agreement in classifying images in the 2 following categories: normal + bulging vs focal protrusion + broad-based protrusion + extrusion, according to the CTF nomenclature; or normal + symmetric bulging vs protrusion (focal or broad-based) + hernia (extrusion or sequestration), according to the Nordic nomenclature.