Inter- and intra-examiner reliability of the upper cervical X-ray marking system

This paper investigates the reliability of the upper cervical X-ray marking procedure. The measurement chosen to be examined was atlas laterality. Twenty X-rays were marked by three experienced upper cervical practitioners for the inter-examiner reliability testing, and two of the doctors marked 10 of the films twice for intra-examiner testing. The average measurement for the 60 markings was 1.83 degrees. The average difference between the 3 doctors was 1.05 degrees. The range of error is 57 percent of the average measurement. With interval agreements, it is shown that at the point where all 3 doctors agree 80 percent of the time, the range of error is 2 degrees, this being over 100 percent of the average measurement. The range of error percentages for the 2 intra-examiner tests were 41 percent and 71 percent. It is concluded that with ranges of error of this magnitude any measured differences produced using this system will be just as likely to be from marking error as from actual atlas position change. This should be considered by practitioners who consider these measurements to be objective evidence for demonstrating the results of chiropractic adjustments.