Negative pain management index scores do not necessarily indicate inadequate pain management: a cross-sectional study

The Pain Management Index (PMI) is widely used in the assessment of pain management, and negative scores are traditionally considered to indicate inadequate pain management. However, it is not known whether negative PMI scores are always problematic.

In this prospective observational study, we examined the data of 1156 patients with cancer and pain who were hospitalized in a cancer care hospital in Japan from July 2012 to January 2015 and compared the proportion of patients with PI across various PMI scores in this cohort. We further evaluated the predictive validity of PMI scores for PI using different cutoffs. This study aimed to examine the association between PMI scores and the proportion of patients whose pain interferes with their daily lives (i.e., pain interference [PI]).

We found that lower PMI scores were generally associated with a higher percentage of patients with PI. A smaller proportion of patients with PMI scores of - 1 (567/1550, 36.6%) reported PI compared with those with PMI scores of 0 (788/1505, 52.4%). The sensitivities of PMI scores < - 1 and < 0 for predicting PI were 0.16 and 0.37 and the corresponding specificities were 0.95 and 0.71, respectively.

These findings suggest that PMI scores are inversely associated with the proportion of patients with PI. However, PMI scores of - 1 do not always indicate inadequate pain management; pain management should therefore be evaluated from multiple perspectives.