Grading lumbar foraminal stenosis – Interrater agreement of radiologists and radiology trainees before and after education of a standardised grading scale

Introduction

Lumbar foraminal stenosis is a key contributor to low back pain. Imaging, particularly MRI, is commonly used in the assessment of foraminal stenosis, contributing to treatment planning. The adoption of a standardised grading system to try and improve inter-rater agreement is thought to be of importance. Our study aims to assess the variability of grading lumbar foraminal stenosis amongst reporting doctors, determine whether education about a validated grading scale increases agreement, and determine if these changes persist over time.

Methods

A single-site study involving MRI reporting registrars/radiologists was performed. Participants were shown select MRI images and asked to grade the degree of stenosis in each on a 4-point scale. Subsequently, they were educated about Lee et al's grading system and asked to re-grade the cases 1 and 6 weeks later. The level of agreement was calculated using Gwet's AC1 coefficient and Krippendorff's Alpha.

Results

The baseline level of agreement was substantial (AC1 = 0.71). This decreased to a moderate level of agreement post-intervention (AC1 = 0.575 at 1-week, P-value 0.033 and AC1 = 0.598 at 6 weeks, P-value 0.012). A grading of severe stenosis was 21% more likely 6 weeks post-education.

Conclusion

The baseline agreement at our institution was substantial, thought to be due to the single-centre nature of the study. Moderate agreement was achieved after education regarding the Lee et al.'s scale, in-line with other studies, with changes maintained at 6 weeks, showing retention of the scale parameters. Grading of severe stenosis was more common post intervention.