Visual Analog Scale Scores for Labor Pain

I agree that "to ascribe one single total pain score for an entire labor would present…difficulties to researchers seeking to assess subtle…differences among drugs and/or techniques." However, our article considered not the evaluation of new drugs or therapies, but rather statistical methodologies to measure their cost-effectiveness as labor analgesics. Consideration of both the magnitude and duration of pain (total pain) relief provided by a drug or therapy is necessary to perform a cost-effectiveness analysis. Additional studies are required to assess patients' relative valuations for different magnitudes and durations of pain. The visual analog scale is a vertical or horizontal line, usually 10 cm in length, with descriptive words such as "no pain" and "worst pain imaginable" written at the end points. The patient marks the line at the point that they consider represents the amount of pain they are experiencing at that moment. The psychometric basis for the visual analog scale relates to power functions relating (i) the subjective magnitude of pain to the true magnitude of the pain stimulus and (ii) the subjective magnitude of linear distance to the true distance along a line. In contrast, the Apgar score assigns numerical values to nonoverlapping clinical categories. The two are different from a psychometric perspective. Franklin Dexter, MD, PhD Department of Anesthesia; University of Iowa; Iowa City, IA 52242