Scales for measuring labor pain: A literature review

Abstract

Purpose
The purpose of this study was to examine and summarize the current state of knowledge regarding the scales used to assess labor pain, the manner in which they are used, their validity and reliability.
Method
A literature search was conducted using three key electronic databases (Igaku Cyuou Zasshi, Pubmed and CINAHL) and the reference lists from the selected articles. To integrate the available knowledge, all literature published until May 2010, written in Japanese or in English, and that used a scale for measuring labor pain for women during and after childbirth was sought, yielding 50 articles for review.
Results
The following scales were those most often used in the literature for measuring the intensity of labor pain: Visual analogue scale (VAS), Numerical rating scale (NRS), Face rating scale (FRS) and Verbal rating scale (VRS). In addition, the Mcgill pain questionnaire (MPQ) was used to measure both the intensity and quality of labor pain. Each of these scales is used during and after delivery.
VAS is a measurement scale that tries to measure the individual amount of pain that a patient feels ranges across a continuum from none to an extreme. In most of the studies reviewed, the VAS was used, as it ensures concurrent validity with PPI of MPQ, discriminant validity, convergent validity, as a measurement of labor pain.
NRS, FRS, VRS and PPI of MPQ are scales that try to measure the pain as a categorization of none, mild, moderate and severe would suggest. PPI has a concurrent validity with VAS but the other scales do not ensure any validity.
However, MPQ ensures factor validity, discriminant validity as a measurement of labor pain, MPQ (Japanese version) needs to be reconsidered for translation and categorization.
All of these scales do not ensure their reliability as measurements of labor pain.
Conclusion
The most common scale for measuring labor pain was the VAS.
However VAS is a validated scale that can measure the individual amount of labor pain, the VAS scores vary by the individual; thus, it is difficult to compare VAS scores between subjects.
VAS, NRS, FRS, VRS and PPI of MPQ do not ensure their reliability as a measurement of labor pain.
MPQ, which is a validated scale to measure both quality and quantity of labor pain, have more difficulty to answer during labor compared with VAS, NRS, FRS, VRS. In Japan, not only improving MPQ Japanese version but also developing Short formed MPQ Japanese version is needed.
Therefore, some caution is required in choosing scales, measuring, and handling to increase the precision of the measurement of labor pain.