To Örebro University

BACKGROUND: Six to nine per cent of all newborn infants require admission to a neonatal intensive care unit (NICU) due to either illness or prematurity. During their stay, these infants are often subjected to many painful procedures that can cause negative long-term consequences. To reduce the negative effects of pain exposure and ensure optimal and safe pain treatment, accurate assessment of pain is necessary. To achieve this, clinicians are dependent on the use of reliable, objective, and standardised clinical rating scales of pain, henceforth referred to as 'rating scales'. Numerous rating scales have been published; however, discrepancies in validity limit their overall applicability in clinical practice and research. Such limitations may lead to an over- or underestimation of pain, resulting in unnecessary sedation or inadequately treated pain, potentially jeopardising infant safety through treatment side effects, including withdrawal symptoms or prolonged discomfort. To date, the majority of rating scales have been developed to assess procedural pain, whilst fewer scales for prolonged pain are available. Premature infants further complicate matters, as they often have a reduced ability to display robust pain behaviour due to their immaturity. Research has also shown that the use of rating scales in clinical practice is suboptimal, due to both inadequate and infrequent implementation alongside inappropriate choice of scale for the specific pain, population, or setting under evaluation. Despite numerous studies investigating the burden of pain in newborn infants, little work has been done to summarise the current evidence on the appropriateness of rating scales for specific types of pain or infant conditions. This has likely been limited by the subjectivity of pain assessment and further complication of assessing such a non-verbal and immature patient population. The immense burden of neonatal pain worldwide has also led to the development of numerous rating scales in various languages, further hindering evidence summation.

OBJECTIVES: To systematically review the literature to compile and describe the development, content, and measurement properties of clinical rating scales for the assessment of pain in newborn infants.

SEARCH METHODS: An Information Specialist systematically searched CENTRAL, PubMed, Embase, and CINAHL. The latest update search is current to July 2023.

SELECTION CRITERIA: We included all study designs that involved the development or testing of a rating scale for assessing pain in newborn infants. We included preterm (born before week 37) and term (born at week 37 or beyond) infants undergoing pain assessment for any medical indication. We also included studies that included healthcare professionals.

DATA COLLECTION AND ANALYSIS: We evaluated clinical rating scales assessing pain in newborn infants using the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) methodology evaluating content validity, structural validity, internal consistency, reliability, measurement error, hypothesis testing, and cross-cultural validation. We used a modified GRADE approach to assess risk of bias, inconsistency, imprecision, and indirectness.

MAIN RESULTS: We included 79 studies involving a total of 7197 infants, 326 nurses, and 12 physicians. Twenty-seven clinical rating scales were used in 26 countries, with 14 studies evaluating preterm infants, 11 on term infants, 46 on both preterm and term infants, four solely on medical staff, and four on preterm and/or term infants plus medical staff. Following the COSMIN checklist, we found all rating scales to be of very low-certainty evidence, raising concerns regarding their validity, reliability, and applicability in this vulnerable population across diverse clinical settings.

AUTHORS' CONCLUSIONS: Clinical staff should be vigilant when applying the currently available neonatal rating scales. Further development of rating scale content and testing for structural validity are necessary and should be prioritised. Together, they determine the content and structure of rating scales, underpin further testing, including reliability, and their prioritisation will make the greatest contribution to the evidence base for rating scales to assess neonatal pain. Collaborative efforts between clinicians and methodology experts will prevent methodological pitfalls and contribute to improving the validity and reliability of pain-rating scales in neonatology.