Table 9.

Randomized studies evaluating a placebo response rate using saline control injections

Study	Number of patients	Study design	Type of blocks (placebo arm)	Placebo response or false-positive rate*	Comments
Revel et al 45	80–38 who received placebo	Randomized, parallel group	IA with 1 mL saline	18% placebo response	Response defined as >75% relief.
Cohen et al 18	229–47 who received placebo	Randomized, three-arm parallel group	MBB with 0.5 mL saline	30% placebo response	Response defined as >50% relief.
Lord et al 209	50 patients with whiplash	Randomized, three-period crossover	Cervical MBB with 0.5 mL bupivacaine, lidocaine and saline	40% placebo response, false-positive rate (concordant relief with LA blocks but positive response to placebo) 19%	Response defined as longer pain relief (complete or profound) with bupivacaine than lidocaine, and a negative response to saline. False-negative rate (positive but discordant response to LA injections but negative response to placebo) 32%. Sensitivity 54%, specificity 88%.
Dias da Rocha et al 173	104	Patient-blinded, one-way crossover	Lumbar MBB with 0.5 mL saline, and if negative, lidocaine	16% placebo response	Response defined as ≥50% relief. All patients received saline and if negative, lidocaine MBB after 10 min.
Schütz et al 146	60	Single-blind, three-way crossover	Bilateral lumbar IA injections with 1.5 mL of mepivacaine (verum), saline (placebo) or extra-articular needle placement without injection (sham)	Sham and placebo groups had 20% and 38% response rates, respectively, at 1 hour	Response defined as >2-point decrease in back pain. Non-inferiority shown between placebo and verum injection.

Injections in lumbar spine unless specified.

*False-positive rate based on positive response to verum and negative response to sham injection.

IA, intra-articular; LA, local anesthetic; MBB, medial branch block.