Positive Predictive Values of Lumbar Spine Magnetic Resonance Imaging Findings for Provocative Discography

Abstract

The purpose of this study was to calculate the positive predictive value (PPV) of lumbar spine magnetic resonance imaging (MRI) findings for a painful disc using provocative discography. Lumbar spine discography records and prediscography MRIs of 736 patients (2457 discs) who underwent discography for diagnostic purposes from 2003 to 2007 were retrospectively reviewed in an Institutional Review Board-exempt and Health Insurance Portability and Accountability Act-compliant protocol. Each level was identified as having high-intensity zone (HIZ) disc, disc protrusion, disc extrusion, or combination (any herniation type), disc bulge, disc degeneration, and spondylolisthesis. Statistical analysis used a 2 × 2 contingency table of significant discography results for each of the MRI variables to calculate P value and PPV with a confidence interval from a binomial distribution. An HIZ disc has a PPV of 0.71 (0.65-0.76, P = 4.31E - 44) for a provocative discography. A disc protrusion has a PPV of 0.79 (0.73-0.83, P = 2.68E - 53). A disc extrusion has a PPV of 0.93 (0.79-0.98, P = 1.34E - 14), a bulge of 0.43 (0.37-0.48, P = 0.002), and a degenerative disc of 0.32 (0.28-0.35, P = 0.08), and spondylolisthesis has a PPV of 0.67 (0.59-0.73, P = 1.70E - 20). A herniation of either type (extrusion or protrusion) has a PPV of 0.80 (0.75-0.84, P = 5.86E - 69). Disc herniations and HIZ discs have high predictive value in identifying a pain generator. An extruded disc herniation has the highest PPV for discogenic pain.