Reliability and validity of the Functional Rating Index in older people with low back pain: preliminary report.

Abstract

The Functional Rating Index (FRI) was developed to provide an assessment instrument which has not only clinical usefulness but also quantifies the patient's current state of pain and dysfunction in a reliable and valid manner for spinal conditions. There is no study on the FRI applied to older people with low back pain (LBP). The primary aim of this study was to evaluate the validity and reliability of the FRI in older people with LBP. A total of 76 subjects aged 65 to 90 years with LBP, of which 37 were cognitively intact and were followed up on a second occasion, were assessed by the FRI, numeric rating scale (NRS), Roland Morris Questionnaire (RMQ) and spinal movement test. Reliability was assessed by statistical analysis of test results for test-retest and internal consistency. To assess construct validity, the FRI was compared with the RMQ. Concurrent validity was assessed using the NRS and spinal mobility test. The FRI demonstrated high internal consistency, with alpha=0.921 for test and alpha=0.901 for retest. Item-scale correlations were between 0.549-0.871. Test-retest correlation was 0.913 (p=0.000). There was very good construct validity between the FRI and the RMQ for test (r=0.663, p<0.000) and retest (r=0.603, p<0.000). The FRI showed high correlation with the NRS (r=0.701, p<0.000 for test; r=0.743, p<0.000 for retest) and no correlation with the spinal movement test (r=0.173, p=0.307 for test; r=0.024, p=0.888 for retest). In this preliminary report, the FRI appears to be easy to administer, seems to have significant validity and reliability, and may be useful in geriatric assessment of older people with LBP.