Objectives: The Multidimensional Symptom Index (MSI) is a 10-item parallel score frequency×interference patient-reported outcome for use in clinical pain research. This manuscript describes results related to measurement stability, discriminative accuracy when screening for major depressive disorder (MDD), and prognostic validity when predicting recovery trajectories after acute musculoskeletal (MSK) trauma.
Methods: Data were drawn from a longitudinal cohort study of adults with acute MSK trauma, supplemented by a secondary sample of adults with chronic pain.
Results: In a sample of n=23 stable participants over a 1-month period, reliability metrics indicated good stability for all 5 subscales (ICC3,1: 0.70 to 0.91). In a mixed acute/chronic sample (n=148), the Number of Symptoms and Nonsomatic Symptoms subscales showed clinically useful discriminative accuracy for MDD screening (area under the curve=0.86 and 0.88, respectively). In n=129 with acute MSK trauma, the Mean Interference and Nonsomatic Symptoms subscales showed significant prognostic validity for classifying participants into "recovery expected" or "recovery not expected" groups with 72.5% and 92.2% accuracy, respectively.
Discussion: The MSI holds promise as a tool for evaluating change, screening for MDD, and identifying those at high or low risk of poor recovery. The results favor sensitivity over specificity. The labile nature of the acute pain symptoms and a truncated distribution of Nonsomatic Symptoms scores in that group both require some caution in interpretation. The MSI appears to be a potentially useful tool for rapid pain phenotyping, evaluation, and quick screening purposes in clinical practice.