Psychometrics of the Neonatal Oral Motor Assessment Scale

Full attainment of oral feeding is one of the most complex tasks of infancy1,2 and one of three criteria required for discharge from the neonatal intensive care unit (NICU).3 Infants in the NICU are often delayed in oral feeding and are at increased risk of oral-motor dysfunction, non-organic failure to thrive, and dysphagia.4–6 Additionally, poor feeding in neonates has been associated with subsequent developmental delay and feeding difficulties in childhood.4 Children with feeding complications have higher incidences of brain injury, and often experience long-term motor, behavioral, and cognitive dysfunction.5–9 Early identification of these problems is important to enable interventions to optimize function,10 and relies on the availability of valid and reliable assessment tools. The Neonatal Oral Motor Assessment Scale (NOMAS), developed by Marjorie Meyer Palmer in 1985, is a widely used neonatal feeding evaluation.2,7,11–13 The tool is not commercially available. Raters are certified through a 3-day course, conducted most often by Palmer. As a requirement set by Palmer, participants are certified at the end of the course if they correctly classify five videotaped feedings as ‘normal’, ‘disorganized’, or ‘dysfunctional’. The NOMAS is the only available neonatal feeding evaluation that can be used with term or preterm infants and with infants who are breast or bottle-fed.1 The NOMAS is a 28-item observational checklist of tongue and jaw movement. Following observation of non-nutritive sucking, the first two minutes of oral feeding are evaluated. Feeding is classified as normal, disorganized, or dysfunctional.11 Using the NOMAS, normal defines an infant demonstrating coordination of suck–swallow–breathe responses and feeding efficiency.13 Infants who demonstrate difficulty coordinating suck–swallow–breathe are classified as disorganized. Any abnormal movement interrupting the feeding process leads to a classification of dysfunctional.11,12 Dysfunctional characteristics include excessively wide jaw excursions interrupting the seal on the nipple, lateral jaw deviation, a flaccid/retracted tongue, or total absence of movement.13 Though the NOMAS was developed over 20 years ago, there is limited research investigating its psychometric properties.1 One study reported that at age 2 years, 100% of infants classified as normal on the NOMAS will not have developmental delay, and 100% of infants classified as dysfunctional will have developmental delay.14 The ability of the NOMAS to predict developmental delay in infants categorized as normal or dysfunctional is cited during the certification course. However, this study assessed 17 infants and was retrospective, with many confounding factors, weakening its results and implications. Another study found the NOMAS to have modest internal consistency within the normal and disorganized categories (Cronbach α>0.70) and acceptable convergent validity for infants 32 to 35 weeks' postmenstrual age (Spearman’s r=0.51–0.69).2 The study did not include calculations for the dysfunctional category, and called for further investigation of the NOMAS. Another study found the interrater reliability to be ‘moderate’ to ‘substantial,’ with kappa (κ) =0.40 to 0.65 and intrarater reliability to be variable at κ=0.33 to 0.95. This was considered unacceptable for a diagnostic tool.12 The NOMAS has been associated with 12-month outcome; infants categorized as normal performed better on developmental tests than infants persistently categorized as disorganized.9 However, this study excluded infants with cerebral injury, which is common in preterm infants and other high-risk populations. The ability of assessments like the NOMAS to identify those in need of early intervention could enhance the short and long-term care of preterm infants, and help minimize the effects of feeding related morbidities.10 It is therefore necessary to further investigate the psychometric properties of the NOMAS to provide clinicians with accurate information, and to work toward developing standardized and reliable tools to assess feeding in high-risk populations. The aim of this study was to evaluate the concurrent and predictive validity of the NOMAS, as well as its interrater and intrarater reliability.