Correlation of the Critical Care Pain Observation Tool and Numeric Rating Scale in Intensive Care Unit Patients

Purpose We sought to determine the correlation between the Numeric Rating Scale (NRS) and Critical-Care Pain Observation Tool (CPOT) to determine whether clinical factors modified the relationship between NRS and CPOT assessments. Materials and Methods We included nonventilated adults admitted to the MICU or SICU who could self-report pain and had at least 3 paired NRS and CPOT assessments. We performed Spearman correlation to assess overall correlation and performed proportional odds logistic regression to evaluate whether the relationship between NRS and CPOT assessments was modified by clinical factors. Results Nursing staff performed NRS and CPOT assessments every 4 h in 1302 patients, leading to 61,142 matched assessments. We found that the NRS and CPOT have a Spearman correlation coefficient of 0.56 and an intraclass correlation coefficient of 0.32 in intensive care unit patients. Factors that modified the relationship between the NRS and CPOT included the presence of delirium (P < .001) and lower mean daily Richmond Agitation Sedation Scale (<0.001). Conclusions The correlation coefficient between the NRS and the CPOT was found to be 0.56. The presence of delirium, decreased level of arousal, modified the relationship between the NRS and CPOT. Self-reported and behavioral pain assessments cannot be used interchangeably in critically ill adults.