Relying on nerve blocks to diagnose arthritis-related back pain prior to treatment may result in excessive tests, delay pain relief and increase costs, according to a study published in the August edition of Anesthesiology.

Current protocols use a single or double diagnostic nerve block to confirm arthritis as the cause of back pain and then proceed to radiofrequency (RF) denervation to interrupt nerve-pain signals, explained lead author Steven P. Cohen, MD, associate professor of anesthesiology and critical care at the Johns Hopkins University School of Medicine in Baltimore.

Because diagnostic blocks are associated with false-positive rates in the 20-40 percent range, some providers recommend two blocks, with the second as a confirmatory block, prior to treatment.

The approach is wrong, asserted Cohen. “If we do the radiofrequency procedure first, we’re going to help more people and we’re going to save money.”

Cohen led a randomized, multicenter study from January 2007 to April 2009 that divided 151 patients with lumbar pain that fit the criteria for arthritis into three treatment paradigms. Group 0 proceeded to RF denervation based on clinical findings without nerve blocks; group 1 underwent RF denervation after a positive response to one diagnostic nerve block; and group 2 proceeded to RF denervation treatment only after positive response to two nerve blocks.

Thirty-three percent of group 0 patients achieved a successful outcome, defined as 50 percent pain relief with a positive perceived global effect persisting for three months. In comparison, 16 percent of group 1 and 22 percent of group 2 patients obtained similar relief in the same time period. Denervation success rates were 33, 39 and 64 percent in groups 0, 1 and 2, respectively. Costs per successful treatment in groups 0, 1 and 2 were $6,286, $17,142 and $15,241, respectively.

The study adds a new wrinkle to the ongoing debate about whether to perform one or two diagnostic nerve blocks prior to RF treatment. Some providers prefer the two-block protocol to reduce the risk of false-positive relief from a single block, but Cohen stresses that pain relief should take precedence over diagnostic accuracy. The cost difference among the approaches further supports the straight-to-denervation approach.

“Based on this simple model of cost-effectiveness proceeding straight to radiofrequency denervation without any diagnostic blocks is associated with both the lowest cost per successful procedure and the highest number of total successful procedures,” concluded Cohen. However, he cautioned that the framework may not be generalizable because patients in the study were screened to ensure maximum compliance.