Inter-Examiner Agreement of the National Upper Cervical Chiropractic Association Analysis of the Atlas Subluxation Complex in a 3-View Upper Cervical Radiographic Series

Objective

The purpose of this study was to measure the inter-examiner agreement between radiograph markings of 2 National Upper Cervical Chiropractic Association board-certified chiropractors.

Methods

Two chiropractic examiners who had standardized training marked and analyzed 254 conventional orthogonal radiographic film sets. The level of agreement and potential biases in their measurements were assessed using intraclass correlation coefficients for absolute agreement and Bland-Altman plot analyses.

Results

There was 96.1% agreement between the examiners in the measurements of the side of atlas laterality and 94.5% for atlas rotation. The intraclass correlation coefficient was 0.95 (95% CI, 0.93-0.96) for atlas laterality and 0.92 (95% CI, 0.89-0.94) for atlas rotation. The mean difference in the measurement between the 2 examiners was −0.11, P = .12 for atlas laterality and 0.05, P = .55 for atlas rotation. Neither atlas laterality nor atlas rotation measurements were significantly different from zero. Bland-Altman plots were not suggestive of any proportional biases in the 2 measurements.

Conclusion

Results of this study show almost perfect agreement between 2 trained chiropractic examiners, with no apparent proportional bias in the analysis of conventional orthogonal radiographic film sets.