Interobserver reproducibility in the interpretation of bone scans from patients suspected of having reflex sympathetic dystrophy.

Objective: This work was undertaken to identify scintigraphic patterns obtained in patients suspected of having reflex sympathetic dystrophy (RSD), now often referred to as complex regional pain syndrome, whose interpretations could be difficult.

Methods: Ten patients had bone scans because of clinical suspicion of RSD in the lower legs. They were selected retrospectively to have a wide sample of scintigraphic patterns. The radionuclide images and a multiple-choice questionnaire were presented as a PowerPoint file that was sent electronically on the Internet to 54 Belgian nuclear medicine physicians. They had to determine whether the images were in favor of the diagnosis of RSD.

Results: Twenty-eight answers (52%) were received. There was near-complete interobserver agreement for perfectly normal scans, for scans showing diffuse uptake with enhancement of periarticular activity, and for scans showing only focal hyperactivity at the site of previous trauma. Results were more discordant when the hyperactivity was mild and when there was a diffuse hypoactivity, with or without focal hyperactivity.

Conclusion: This study shows that using very simple methodology, it is possible to identify some scintigraphic patterns in which there is disagreement among observers and whose interpretations vary. As the results are returned to the participants, they can compare their own interpretations with those of their peers. This aspect could be useful in continuing education in medical imaging.