Intra- and inter-observer reliability of the Cobb measurement by chiropractic interns using digital evaluation methods.

Introduction: It is important to create a body of evidence surrounding the reliability of certain diagnostic criteria. While the reliability of the Cobb measurement is well established with various licensed health care professionals, this study aims to determine the inter- and intra-observer reliability of the Cobb Measurement among chiropractic interns.

Methods: Fourteen chiropractic interns analyzed 10 pre-selected digital spinal radiographs on a Picture Archiving and Communication System (PACS) in two separate rounds of observation. The participants indicated their choice of end vertebra and Cobb Measurement in each round of observation. Agreement on vertebral levels selected was estimated using percentage agreement. Intra-observer reliability was estimated using the Pearson r correlation coefficient, and inter-observer correlation was estimated using the Inter-Class Coefficient (ICC).

Results: The range of percentage agreement on vertebral level selection was 0.36 - 0.79. The Pearson r correlation coefficient for round 1 and round 2 was 0.79. The ICC (3,1) was 0.79 (round 1), and 0.70 (round 2).

Conclusion: Less than optimal agreement on end vertebrae selection was found between observers. Intra- and inter-observer reliability of the Cobb Measurement was 'excellent' (round 1) and 'good' (round 2).