Introduction: The Brief Pain Inventory (BPI)–Facial is a reliable tool for measurement of pain in patients with trigeminal neuralgia (TN). However, a statistically significant change in this score does not necessarily represent a meaningful difference to patients. The goal of this study is to calculate the minimal clinically important difference (MCID) for TN.
Methods: This study is a single center, single surgeon cohort analysis of all patients seen in the office with a diagnosis of facial pain between 2006- 2011. The BPI-Facial was administered at the first visit and via follow-up phone calls. The patient global impression of change (PGIC) was used as a gold standard, external criterion. Three methods were used to calculate the MCID: 1) mean change score, 2) standard error of measurement (SEM), and 3) optimal cut-off point. To date, 144 interviews of total 576 patients have been conducted for subjects.
Results: Using three methods of calculation (mean change score, SEM, ROC analysis, respectively), we calculated the MCID as follows. For NRS-averaged, the MCID values were 3.5, 1.1, and 2.75. For the NRS at the worst, the MCID values were 4.7, 1.6, and 3.0. For the BPI-general, the MCIDs were 3.5, 1.2, and 3.2. For the BPI-facial, MCID values were 4.0, 1.5, and 4.0. The SEM method appeared to underestimate the MCID in all groups.
Conclusions: An early step in the validating an outcome tool like the BPI-Facial is calculating the MCID. We have calculated the MCID using three methods and conclude that two of the methods are best suited for TN. Future steps will involve prediction of benefit stratified by procedure type, facial pain classification, and other predictor variables. We encourage practitioners who see patients with TN to measure pain before and after treatment using the BPI-Facial.
Patient Care: Our research validates the use of the Brief Pain Inventory (BPI) -Facial in the clinical setting. Administering the BPI-facial at initial visit and post-procedurally in patients with facial pain disorders will allow practitioners to more accurately evaluate clinical change seen in these patients.
Learning Objectives: The importance of determining the minimal clinically important difference (MCID) seen in trigeminal neuralgia patients. The calculation of the MCID is also an important step in validating outcome tools like the BPI-facial.
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