Can neuropathic screening tools be used as outcome measures?

OBJECTIVE: To examine whether the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) screening tool can satisfy Rasch model expectations and therefore be transformed into an interval level measurement scale, suitable for use as an outcome measure in clinical studies.
DESIGN: Rasch analysis (using the software RUMM2020) of LANSS data from both a random selection of all chronic pain patients and also specific chronic pain diagnostic categories. PATIENTS: Original LANSS data from a previous study of 2,480 patients with chronic pain were used. Specific diagnostic groups examined included diabetic neuropathy, postsurgical pain, osteoarthritis, posttraumatic injury, and low back pain. OUTCOME MEASURES: The following assessments were made: fit to the Rasch model, scale reliability, scale multi-dimensionality, and differential item functioning.
RESULTS: The overall fit to the Rasch model was only acceptable in two groups; diabetic neuropathy and chronic postsurgical pain. For these groups, the scale is unidimensional (measures a single construct) and there is no evidence of differential item functioning across gender and age groups. The scale only has reliability consistent with use at the group level.
CONCLUSIONS: Neuropathic screening tools such as the LANSS have been used as outcome measures in clinical studies. Rasch analysis demonstrates that the LANSS can be used as such in specific populations of patients with neuropathic pain, however it's reliability in this context does not support use at the individual level and it cannot be used as a generalised measurement tool across pain diagnostic groups. The LANSS remains primarily a diagnostic tool. Wiley Periodicals, Inc.