How high should total pain-relief score be to obviate the need for analgesic remedication in acute pain? Estimation using signal detection theory and individual-patient meta-analysis

Background: A pain relief score 50% of the maximum is often used as a clinically meaningful outcome in meta-analyses of analgesic trials. This arbitrary value requires validation. Objective: To determine the optimum pain relief score for predicting pain relief sufficient to obviate the need for analgesic remedication in acute post-surgical pain. Design: Individual-patient meta-analysis of randomized controlled trials and use of signal detection theory to identify the optimum cut-off point on the total pain relief score (TOTPAR). Analgesic remedication was used as the clinical outcome. Data sources: Seven parallel-group, active and placebo-controlled trials of minor analgesics. Results: The predictive value of the TOTPAR score [expressed as a percentage of the maximum score (%maxTOTPAR)] for remedication was excellent for all the trials. The pooled estimate of the area under the receiver operating curve, an index of discriminative power, was outstanding 0.96 (95% CI 0.95-0.97). The pooled estimate of the optimal %maxTOTPAR for predictive purposes was 44.11 (95% CI 44.00-44.23). Conclusion: The analysis suggests that the arbitrary 50% cut-off point TOTPAR score often used in meta-analyses of analgesic trials in dental pain is reasonably acceptable. This is different to the 33% cut-off point reported for analgesic trials of acute breakthrough cancer pain and some chronic pain states such as diabetic neuropathy and postherpetic neuralgia. These differences deserve careful consideration when reading reports of analgesic trials and meta-analyses. Remedication itself should be considered as the preferred outcome measure for analgesic trials.