Objectives: This is a protocol for a Cochrane Review (diagnostic). The objectives are as follows:. The objective of this review is to assess the diagnostic accuracy of red flags used to screen for vertebral fracture in patients presenting with low back pain. Where possible, we will report the results of red flags separately for different types of vertebral fracture as follows. Osteoporotic vertebral compression fracture Vertebral traumatic fracture Vertebral stress fracture. Secondary objectives The secondary objective of this review is to assess the influence of sources of heterogeneity on the diagnostic accuracy of red flag tests, if appropriate. In particular, we will assess the healthcare setting (e.g. primary, emergency, or secondary care) and the different types of vertebral fracture (i.e. osteoporotic vertebral compression fracture, vertebral traumatic fracture, and vertebral stress fracture. We will also assess mean age at different cut-off thresholds (e.g. > 50 years of age versus > 70 years of age) across different studies, as this has previously been shown to influence results.