Assessment of Pain During Medical Procedures: a Comparison of Three Scales

Objective: Pain assessment is crucial to pain research. Knowledge about the strengths and weaknesses of pain measures is important to the continued advancement of our understanding of pain. The purpose of the present study was to compare the validity and utility of three measures of pain intensity during a medical procedure known to produce pain: an abortion.

Design: Assignment to one of three pain intensity assessment instruments, which were subsequently used to assess pain during an abortion procedure. Comparison of the relative sensitivity of the measures to assess changes in pain using a series of repeated measures analyses of variance. The relative utility of the measures was compared by examining the rates of accurate responses to each.

Subjects: Fifty-eight women presenting for a first-trimester abortion.

Measures: Visual analog scale (VAS), the verbal 11-point Box Scale (Verbal BS-11), and the 21-point Box Scale (BS-21).

Results: All three pain intensity measures detected changes in pain during the abortion procedure. Rates of incorrect responses were higher for the Verbal BS-11 and the VAS than for the BS-21.

Conclusions: The results supported the validity of each of the three measures used, although some superiority for the BS-21 over the Verbal BS- 11 and VAS exists. Patients had some difficulty completing the paper-and-pencil VAS during the procedure. In addition and consistent with previous research, some patients treated the Verbal BS-11 as a 21-point scale by responding with numbers between two whole numbers on the 0-10 measure. Overall, practical issues led us to conclude that the BS-21 is an excellent choice for assessing real-time abortion pain.