The use of the Visual Analogue Scale for the assessment of labour pain: a systematic review.

Background: The Visual Analogue Scale has been frequently used to assess parturients' pain intensity, but the psychometric properties of this scale have not been critically reviewed. In addition, limited research has been undertaken to investigate whether this is the most appropriate pain measurement tool in the obstetrical care setting.

Objectives: The overall objective of this review was to measure the psychometric properties (i.e. reliability, validity, sensitivity and specificity) of pain assessment tools that are used to assess women's childbirth pain.

Inclusion Criteria: Types of participants Pregnant women at term (37-42 weeks gestation) who delivered in the hospital setting with cervical dilation from 0cm to 10cm were included.Types of intervention(s)/Phenomena of interest The Visual Analogue Scale and other pain measurement tools.Types of outcomes Reliability, validity, sensitivity and specificity of the pain measurement tools.Types of studies Randomised controlled trials (RCT) that examined the psychometric properties of the Visual Analogue Scale and other measurements for the assessment of labour pain were included. Due to a limited number of RCT on this subject, papers using secondary analysis, descriptive, correlational and comparative designs were also included.

Search Strategy: A three-step search strategy was utilised in this review. An initial limited search of MEDLINE and CINAHL was undertaken, followed by an analysis of the text words contained in the title and abstract, and of the index terms used to describe the article. A second search using all identified keywords and index terms was then undertaken and was extended to other relevant databases. Thirdly, the reference lists of all identified reports and articles were searched for additional studies.

Methodological Quality: Papers selected for retrieval were assessed by two independent reviewers for methodological validity prior to inclusion in the review using the standardised critical appraisal instruments from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument (JBI-MASTARI).

Data Collection/extraction: MAStARI was not used to extract data in this review as predetermined in the protocol because both of the reviewers were in agreement that the data should be extracted by a tool which focuses on the psychometric properties assessment according to the objectives of this review. Therefore, a Data Extraction Form for Psychometric Assessment was developed to extract data from papers included in the review.

Data Synthesis: Four studies were included in this review: 1 RCT, 2 quasi experimental studies and a cross-sectional descriptive study. As the included studies utilised different study designs and collected data at different times, data were unable to be combined in meta analysis and are presented in narrative synthesis.

Results: Four studies were included in the review. The evidence on the psychometric properties of the labour pain scales is sparse; therefore, the use of the Visual Analogue Scale for the assessment of labour pain is currently not supported by the evidence of this review. There was evidence that showed that the use of the Visual Analogue Scale in repeated measures of labour pain, such as increasing pain, can result in inconsistency and have a 'ceiling effect'. High correlations were found between several pain scales such as Visual Analogue Scale, Box Numerical Scale and Verbal Rating Scale providing insights into the interchangeability between the scales in the obstetrical setting. In addition, the findings also highlight that at present, there is no gold standard to measure pain during labour.

Conclusions: Implications for research There is a need for more and better-designed studies to focus on the use of the pain measurement tools for labour pain in the obstetrical care setting. Further research to address the need for a new labour pain scale that will enhance labour pain management is required.Implications for practice Healthcare professionals should take note of the limitations when using the Visual Analogue Scale to assess childbirth pain, such as inconsistency of results and the 'ceiling effect'. To implement the most appropriate tool for an individual parturient, nurses need to be aware of those available and their limitations, since there is currently no gold standard measure.