The brief pain inventory-Interference Subscale has acceptable reliability but questionable validity in acute back and
Caitlin M P Jones1, Chung-Wei Christine Lin1, Joshua Zadro1
1Sydney Musculoskeletal Health, The University of Sydney, The Institute for Musculoskeletal Health, Sydney Local Health District, Level 10 N KGV Building, Missenden Rd, Camperdown 2050, Sydney, NSW, Australia.
Background:
The Brief Pain Inventory-Interference Subscale (BPI-IS) is a subscale of the BPI assessment tool developed to rapidly assess the impact of a person's pain on their function. It is uncertain whether it has one or two factors, and whether it has acceptable clinimetric properties in a mixed spinal pain (back and/or neck) population.
Objectives:
To determine the clinimetric properties of the BPI-IS in a population with mixed spinal pain.
Methods:
We completed a clinimetric evaluation with a test-retest design, factor analysis, and hypothesis testing. We used data collected for a randomised clinical trial including a population presenting to primary care or emergency departments with acute spinal pain (back and/or neck).
Results:
Confirmatory factor analysis better supported the two-factor model of the BPI-IS (physical interference factor and affective interference factor) as compared to the one-factor model. Both one and two-factor models had acceptable reliability (high internal consistency and no evidence of floor or ceiling effects). Both models failed to reach our a-priori thresholds for acceptable construct (cross sectional) validity, and responsiveness (longitudinal validity) in either back or neck pain populations.
Conclusion:
The BPI-IS has two factors and both have acceptable reliability, but tests for validity did not reach our a priori thresholds for acceptability (construct validity and responsiveness). The BPI-IS may not be suitable to measure the impact of pain on function in back and neck pain populations.
