Table 1 Inter-rater reproducability results for the initial group of three trainee clinicians for 14 pathoanatomic categories across the four coding rounds, expressed as a Kappa co-efficient and percentage agreement with 95% confidence intervals (95% CI)

Intervertebral disc degeneration

Prevalence*

Kappa

Percentage agreement

71.7% (50.2-93.1)

0.66 (0.54-0.77)

80.8% (73.8-87.9)

94.0 (92.0-96.0)

0.94 (0.84-1.00)

95.8 (92.3-99.4)

80.0 (80.0-80.0)

n/a

98.2 (95.8-100.0)

83.3 (80.1-86.6)

0.91 (0.80-1.00)

97.5 (94.7-100.0)

Intervertebral disc bulge

Prevalence

Kappa

Percentage agreement

73.3% (70.1-76.6)

0.91 (0.78-1.00)

95.0% (94.7-100.0)

87.0 (83.1-90.9)

0.86 (0.76-0.90)

92.5 (87.7-97.2)

70.0 (70.0-70.0)

1.00 (0.87-1.00)

100.0

48.3 (45.1-51.6)

0.89 (0.76-1.00)

99.2 (97.5-100.0)

Intervertebral disc herniation

Prevalence

Kappa

Percentage agreement

40.0% (34.3-45.7)

0.91 (0.73-1.00)

97.5% (94.7-100.0)

61.0 (59.0-63.0)

1.00 (0.85-1.00)

100.0

40.0 (40.0-40.0)

0.98 (0.87-1.00)

96.5 (93.1-99.9)

45.0 (45.0-45.0)

1.00 (0.82-1.00)

100.0

Nerve root compromise

Prevalence

Kappa

Percentage agreement

13.3% (4.7-22.0)

n/a

97.5% (94.7-100.0)

42.0 (31.9-52.1)

0.74 (0.49-1.00)

94.2 (90.0-98.4)

31.7 (23.0-40.3)

0.63 (0.45-0.81)

93.0 (88.3-97.7)

18.3 (15.1-21.6)

1.00 (0.75-1.00)

99.2 (97.5-100.0)

Modic change type 1

Prevalence

Kappa

Percentage agreement

26.7% (23.4-29.9)

0.86 (0.68-1.00)

95.0% (91.1-98.1)

18.0 (15.6-20.4)

0.86 (0.60-1.00)

98.3 (96.0-100.0)

20.0 (20.0-20.0)

1.00 (0.82-1.00)

100.0

18.3 (15.1-21.6)

0.86 (0.60-1.00)

100.0

Modic change type 2

Prevalence

Kappa

Percentage agreement

25.0% (19.3-30.7)

0.76 (0.51-1.00)

97.5% (94.7-100.0)

10.0 (5.6-14.4)

n/a

98.3 (96.0-100.0)

20.0 (20.0-20.0)

1.00 (0.82-1.00)

100.0

5.0 (5.0-5.0)

n/a

100.0

Spondylolisthesis

Prevalence

Kappa

Percentage agreement

20.0% (20.0-20.0)

n/a

97.5% (94.7-100.0)

19.0 (17.0-21.0)

1.00 (0.75-1.00)

100.0

10.0 (10.0-10.0)

1.00 (0.82-1.00)

100.0

0.0 (0.0-0.0)

n/a

100.0

Stenosis

Prevalence

Kappa

Percentage agreement

6.7% (3.4-9.9)

n/a

97.5% (94.7-100.0)

23.0 (20.6-25.4)

0.84 (0.59-1.00)

99.2 (97.5-100.0)

25.0 (25.0-25.0)

0.95 (0.74-1.00)

99.1 (97.4-100.0)

0.0 (0.0-0.0)

n/a

100.0

Scoliosis

Prevalence

Kappa

Percentage agreement

25.0% (25.0-25.0)

1.00 (0.82-1.00)

100.0%

6.0 (4.0-8.0)

n/a

95.0 (91.1-98.9)

5.0 (5.0-5.0)

n/a

99.1(97.4-100.0)

5.0 (5.0-5.0)

n/a

100.0

Osteophytes

Prevalence

Kappa

Percentage agreement

5.0% (5.0-5.0)

n/a

100.0%

1.0 (0.0-3.0)

n/a

100.0

10.0 (10.0-10.0)

n/a

99.1 (97.4-100.0)

10.0 (10.0-10.0)

1.00 (0.75-1.00)

99.2 (97.5-100.0)

Facet joint arthrosis

Prevalence

Kappa

Percentage agreement

0.0% (0.0)

n/a

100.0%

14.0 (12.0-16.0)

0.68 (0.42-0.93)

95.0 (91.1-98.9)

20.0 (20.0-20.0)

1.00 (0.82-1.00)

100.0

5.0 (5.0-5.0)

n/a

100.0

Endplate irregularities

Prevalence

Kappa

Percentage agreement

^#

1.0 (0.0-3.0)

n/a

99.2 (97.5-100.0)

25.0 (19.3-30.7)

1.00 (0.82-1.00)

98.2 (95.8-100.0)

18.3 (11.8-24.9)

0.74 (0.56-0.92)

97.5 (94.7-100.0)

Red flags

Prevalence (%)

Kappa

Percentage agreement

^#

0.0 (0.0-0.0)

n/a

100.0

8.3 (1.8-14.9)

n/a

98.2 (95.8-100.0)

0.0 (0.0-0.0)

n/a

100.0

High intensity zone

Prevalence (%)

Kappa

Percentage agreement

^#

15.0 (11.9-18.1)

0.84 (0.59-1.00)

99.2 (97.5-100.0)

26.7 (20.1-33.2)

0.85 (0.67-1.00)

98.2 (95.8-100.0)

25.0 (25.0-25.0)

1.00 (0.82-1.00)

100.0