COMFORT scale: a reliable and valid method to measure the amount of stress of ventilated preterm infants

OBJECTIVE: Assessment of clinimetric properties and diagnostic quality of a stress measurement scale (COMFORT scale). DESIGN: Sample of an open population. SETTING: Neonatology department (Neonatal Intensive Care Unit), Academic Medical Centre/Emma Children's Hospital, Amsterdam, The Netherlands. METHOD: One clinical expert and 9 observers observed ventilated premature born babies simultaneously. Criterion validity was assessed by correlating the COMFORT scale with the clinical judgment regarding the amount of stress. Interobserver reliability was assessed on the clinical judgment as well as on the COMFORT scale. Diagnostic qualities were evaluated with a ROC curve. RESULTS: On 19 ventilated prematurely born babies (mean gestational age 30 weeks, mean birth weight 1385 gm), one clinical expert and 9 observers made 30 paired observations. The criterion validity of the COMFORT scale was good (Pearson's r of 0.84). The interobserver reliability of the clinical judgment was very good (weighted Kappa 0.84). The interobserver reliability of each item varied from good to almost perfect (weighted Kappa of 0.64 for muscle tone to 1.00 on heart rate). The reliability of the total COMFORT scale score was satisfying (intra-class correlation coefficient of 0.94). The diagnostic quality of the COMFORT scale was excellent, at a cut-off point of 20 the sensitivity was 100 percent, the specificity was 77 percent, and the area under the curve (AUC) of 0.95. CONCLUSION: In this first evaluation, the COMFORT scale appears to be a valid and reliable measurement tool to assess the stress of ventilated prematurely born babies