Methodological challenges in studying recurrence of low back pain.

Recurrences of low back pain (LBP) have been shown to be both frequent and costly, with reported recurrence rates ranging from 5 to 82%. Numerous methodological approaches have been developed to identify recurrence but there has been no standardized definition of LBP recurrence or required follow-up time. The objective of this study was to compare the methodological approaches used to analyze LBP recurrence in seminal contributions and to describe the differences in definitions of LBP recurrence and follow-up structure. Twelve seminal articles were identified for review during which four types of LBP recurrence definition and two types of follow-up structure were recognized. Definitional and follow-up differences considerably contributed to variations in computed recurrence rates due either to measurement or other methodological shortcomings, such as loss to follow-up and sick person effect. The results suggest that there is a need to develop a standardized definition of LBP recurrence and a standardized approach to follow-up to allow direct comparisons of published research findings. The use of alternative definitions is also likely to impact analyses of risk factors contributing to LBP recurrence and direct and indirect costs associated with treating LBP.