Agreement of self-reported items and clinically assessed nerve root involvement (or sciatica) in a primary care setting

INTRODUCTION: We analysed baseline measures from an RCT involving adults with low back pain (LBP) with or without referred leg pain, to identify self-report items that best identified clinically determined nerve root involvement (sciatica). METHODS: Potential indicators of nerve root involvement were gathered using a self-reported questionnaire. Participants underwent a standardised physical examination on the same day as questionnaire completion. Self-reported items were compared to a reference standard (clinical diagnosis) using sensitivity, specificity, predictive values, likelihood ratios (LRs), the area under the receiver operating characteristic curve and logistic regression. Two reference standards are presented: one based on a clinical diagnosis of nerve root problems and excluding possible/inconclusive cases (referred to as a confirmatory reference), and the other being inclusive of possible/inconclusive cases (referred to as an indicative reference). RESULTS: Pain below knee was the best single item for diagnostic accuracy with an area under curve (AUC) of 0.67–0.68, which however is slightly less than the ‘acceptable discrimination’. A cluster of three items, including distribution of pain below the knee, leg pain that is worse than back pain, and feeling of numbness or pins and needles in the leg, did improve discrimination to an ‘acceptable’ level with an AUC of 0.72–0.74 in relation to confirmatory and indicative references, respectively. However, the likelihood ratios from the models were reflective of a ‘small’ amount of discrimination. CONCLUSION: In this primary care population seeking treatment for LBP with or without leg pain, we found no clear set of self-report items that accurately identified patients with nerve root pain. When accurate case definition is important, clinical assessment should be the method of choice for identifying LBP with possible nerve root involvement.