Pain intensity measured using a visual-analogue scale from 0 (no pain) to 100 mm (worse pain imaginable).
Measurements of pain intensity:
(1) at baseline (prior to analgesic dose)
(2) at 30 minutes after the dose
(3) at 1 hour after the dose
(4) at 2 hours after the dose
(5) at 3 hours after the dose
(6) at 4 hours after the dose
(7) at 5 hours after the dose
(8) at 6 hours after the dose
pain intensity difference at 3 hours =
= (pain intensity at baseline) – (pain intensity at 3 hours)
pain intensity difference at 6 hours =
= (pain intensity at baseline) – (pain intensity at 6 hours)
A positive number indicates pain relief at time measured.
A zero indicates no change in pain intensity.
A negative number indicates that the pain is worse.
The summated pain intensity difference is the area under the pain curve. For each segment:
area under curve for segment =
= (MIN(intensity 1, intensity 2) * (time interval in hours)) + ABS((0.5) * ((intensity 2) – (intensity 1)) * (time interval))
total area under the curve =
= SUM(areas for all 7 segments from 0 to 6 hours)
