Table 1.

Key terms

Term	Explanation and example
Absolute risk reduction (ARR)	The treatment group difference in the percentages of participants experiencing an event (e.g., the difference in the percentages of “responders” between the treatment and placebo arms).
Analysis of means	Statistically analyzing the between-group difference in mean outcome.
Between-group difference	The difference in mean outcome between two groups. Example: The mean of the change between baseline and week 12 on a 0-10 NRS for participants in the active treatment group minus the same quantity for participants in the placebo group.
Between-group minimal clinically meaningful difference	The between-group difference in an RCT (i.e., amount of additional pain reduction in the treatment group beyond that observed in the comparator group) that is meaningful to patients or other stakeholders. There is no universally accepted difference between treatment and comparator that is considered to be clinically important.
Confidence intervals (CIs)	At a given level of confidence (e.g., 95%), the range of possible values that are expected to contain the true treatment effect. For example, if the RCT were replicated a large number of times, 95% of the 95% CIs from the RCTs would contain the true treatment effect
Cumulative distribution function (CDF)	Plots of the percentage of “responders” in each study arm across the range of possible responses (see Figure 2).
Duration of effect	The length of the treatment benefit.
Explanatory trials	Trials designed to test whether the treatment is efficacious in more highly controlled settings (e.g., in a relatively homogeneous population).
Number needed to harm (NNH)	Identical to NNT, except NNH evaluates percentages of patients with harms.
Number needed to treat (NNT)	The reciprocal of the treatment group difference in the percentages of participants experiencing an event, calculated as 1/ARR. This number can be used, for example, to indicate the number of patients who would need to be treated to find 1 more “responder” in the treatment arm than in the comparator arm.
Power	Probability of rejecting the null hypothesis of no treatment effect when the treatment actually has an effect of a specified magnitude; calculated as 1 – Prob(Type II error).
Pragmatic trials	Trials designed to test whether a treatment that has been shown to have analgesic efficacy is effective in more real-world settings (e.g., in a heterogeneous population, concomitant medications allowed).
Primary outcome	The prespecified measure on which the effect of the treatment is being evaluated.
Relative risk (RR)	The ratio of the participants experiencing an event in the treatment arm to that in the placebo arm (e.g., the percentage of “responders” in the treatment arm divided by the percentage of “responders” in the placebo arm).
“Responder” analysis	A comparison between treatment groups of the percentage of “responders” (i.e., the individuals who have had a certain percentage improvement in pain intensity from baseline to end-of-study).
Treatment risks	All adverse events (AEs) associated with a treatment as identified by subject symptom reports and clinician-observed signs.
Type I error	Probability of rejecting the null hypothesis of no treatment effect (e.g., no treatment group difference in outcome) when the treatment actually has no effect; typically set at α = 0.05.
Type II error	Probability of failing to reject the null hypothesis of no treatment effect when the treatment actually has an effect of a specified magnitude; typically set at β = 0.10 – 0.20.
Within-group difference	The mean change within one treatment group between baseline and a defined follow-up time period. Example: The mean of the change between baseline and week 12 on a 0-10 NRS for participants in the placebo group.
Within-patient minimal clinically meaningful change	The within-person change in pain intensity that is meaningful to the individual. Typically considered to be ≥ 10-20% improvement on the 0-10 NRS, with > 30% improvement on the 0-10 NRS considered moderate improvement, though baseline levels of pain can affect this percentage.

Notes: NRS – numerical rating scale; RCT – randomized clinical trial