Interobserver reliability of the 24-hour schedule in patients with low back pain: a questionnaire measuring the daily use and loading of the spine

Low back pain is a major health problem in western industrialized countries. The 24-Hour Schedule (24HS) is an instrument which intends to obtain insight in the use (ie, posture and applied load) of the back. It consists of a questionnaire, a series of photos, and a registration form. To assess the interexaminer reliability of the 24-Hour Schedule in patients with low back pain. Reliability study. People with low back pain were included in the study. Sample size calculation indicated that 40 participants would be sufficient to answer the research question. Participants were coded to remain anonymous, and after giving informed consent, they completed a questionnaire. Two trained examiners assessed each participant independently. In total, 5 examiners participated. Forty participants were analyzed. In our study population, the use of the back was approximately 10 times more in a flexed position compared to a lordotic position. Flexed activity was registered in all 80 assessments, but in 39 assessments, there was no registration of any activity in a lordotic posture. In only 1 participant (diagnosed with Bechterew’s disease), the use of the back was more in a lordotic than in a flexed posture. The intraclass correlation coefficient of the assessment was 0.81 (95% confidence interval = 0.67-0.89), corresponding with a high level of agreement between the examiners. The interobserver reliability of the 24HS appeared to be high.