The reliability of determining “leg dominant pain”

Background contextPatients with back dominant pain generally have a worse prognosis after spine surgery when compared with patients with leg dominant pain. Despite the importance of determining whether patients with lumbar spine pain have back or leg dominant pain as a predictor for success after decompression surgery, there are limited data on the reliability of methods for doing so.PurposeTo assess the test-retest reliability of a patient's ability to describe whether their lumbar spine pain is leg or back dominant using standardized questions.Study design/settingProspective, blinded, test-retest cohort study performed in an academic spinal surgery clinic.Patient sampleConsecutive patients presenting for consultation to one of three spinal surgeons for lumbar spine pain were enrolled.Outcome measuresEight questions to ascertain a patient's dominant location of pain, either back dominant or leg dominant, were identified from the literature and local experts.MethodsThese eight questions were administered in a test-retest format over two weeks. The test-retest reliability of these questions were assessed in a self-administered questionnaire format for one group of patients and by a trained interviewer in a second group.ResultsThe test-retest reliability of each question ranged from substantial (eg, interviewer-administered percent question, weighted kappa=0.77) to slight (eg, self-administered pain diagram, weighted kappa=0.09). The Percent question was the most reliable in both groups (self-administered, interviewer). All questions in the interviewer-administered group were significantly (p<.001) more reliable than the self-administered group. Depending on the question, between 0% and 32% of patients provided a completely opposite response on test-retest. There was variability in prevalence of leg dominant pain, depending on which question was asked and there was no single question that identified all patients with leg dominant pain.ConclusionA patient's ability to identify whether his or her lumbar spine pain is leg or back dominant may be unreliable and depends on which questions are asked, and also how they are asked. The Percent question is the most reliable method to determine the dominant location of pain. However, given the variability of responses and the generally poorer reliability of many specific questions, it is recommended that multiple methods be used to assess a patient's dominant location of pain.