A Factor Analysis of the COMFORTneo Scale: What Are We Measuring?

Extremely preterm infants (EPT; < 26 weeks) are often exposed to painful and stressful procedures, and in clinical practice it is difficult to distinguish pain from stress. This study investigated whether the COMFORTneo scale can differentiate between these constructs in EPT and older preterm infants (PT; 26-36 weeks' gestational age). We analyzed COMFORTneo scores from 1021 preterm infants admitted to a level IV NICU between 2018 and 2022. Infants were divided into four subgroups: EPT ventilated, EPT non-ventilated, PT ventilated, and PT non-ventilated. Exploratory and confirmatory factor analyses were used to assess the underlying structure of the scale. In addition, a panel of 11 NICU professionals completed a short questionnaire regarding the constructs represented by COMFORTneo items. Exploratory factor analysis indicated a unidimensional structure for EPT infants, whereas two factors emerged in PT infants, with interfactor correlations of r = 0.78 in ventilated infants and r = 0.63 in non-ventilated infants. Confirmatory factor analysis supported these structures, with comparative fit index (CFI) values ≥ 0.96 and root mean square error of approximation (RMSEA) ranging from 0.070 to 0.091. Experts' interpretations of the constructs associated with the identified factors varied across respondents. Overall, the COMFORTneo scale appears to capture a single construct in EPT infants and two related constructs in PT infants. However, NICU professionals did not consistently distinguish between these constructs in practice. These findings highlight the importance of developmentally sensitive interpretation and caution against relying solely on total COMFORTneo scores.