To Örebro University

Background: Numerous clinical studies have aimed at finding a strategy to reduce the pain newborn infants are subjected to by their medical conditions and also by medical and caring procedures. Little is however known about whether the outcome measures in these trials are valid for the specific type of pain or group of infants included in the studies. There are today over 40 published scales, consisting of behavioral or physiological signals or a combination of both. The aim of this study was to evaluate the reporting of pain scales assessments that were most commonly used in all the published trials examining interventions related to neonatal pain.

Methods: A systematic and broad search up to January 2019 was performed in Embase, PubMed, PsycInfo, Cinahl, Cochrane Library, Scopus and Luxid. Randomized and quasi-randomized clinical trials on neonatal pain were included. Title and abstract screening followed by full text screening were performed by two independent researchers using an online tool for the preparation of systematic reviews (Covidence). Disagreements were resolved by a third researcher or in discussions within the group, as recommended in the Cochrane handbook. Data extraction and quality assessment were also performed by two researchers independently. 

Results: The systematic search retrieved 3715 scientific articles. Following screening, 342 studies with a total of 16210 infants were included, reporting data from the use of at least one neonatal pain assessment scale. Ninety per cent of the studies concerned procedural pain where the most frequently used pain scales were PIPP or PIPP-R (43%), followed by NIPS (17%). For ongoing or post-operative pain there was a more unclear pattern with COMFORT (24%) and NFCS (10%) as the most reported. We observed a wide variation of pain scales (Fig 1) and found numerous studies where pain scales were used that were not validated for the studied population or type of pain. In 11 papers self-constructed study-specific scales were used. The most frequent sources of procedural pain were heel lance (28% of the studies) followed by venipuncture (10%) and ROP-screening (5%).

Conclusion: This is the first scoping review reporting systematically how neonatal pain scales are used in clinical trials. There are a few validated pain assessment scales used in most clinical studies. It is crucial to choose an appropriate scale, validated for the type of pain and population of infants included in the study. The inappropriate use of pain scales raises serious concerns on ethical conduct of research and waste of resources.