The General Function Score: a useful tool for measurement of physical disability. Validity and reliability

Abstract

IntroductionThe consequences of low back pain (LBP) for an individual can be generally described and measured on three different levels [6,11,25] Abstract The General Function Score (GFS) is a disease-specific instrument consisting of nine items focusing on strict physical activities of daily living. It is intended as an alternative to the more complex scores of disability (such as the Oswestry Disability Index), serving as a complement to the quality of life instruments in the study of low back pain (LBP). It was developed from an original 17-item questionnaire, of which 11 of the items were tested for criterion validity in an observer-supervised performance test. Two items were excluded from further analysis because of too low a validity. The remaining nine-item GFS was tested for construct validity, reliability, feasibility and responsiveness in six different cohorts: 297 patients with chronic low back pain (cohort 1), an age-and sex-matched control group of 287 randomly allocated Swedish citizens (cohort 2), three separate groups of patients admitted for surgery due to low back disorders (cohorts 3-5) and outpatients with spinal disorders (cohort 6). Correlations were tested with the Spearman Rank correlation coefficient, differences between groups with the MannWhitney test and the internal consistency with the Cronbach's coefficient α. The GFS total scores showed correlations of 0.78, 0.81 and 0.88 in the three aspects of the performance test. The response rate was 98.3-100%. The mean time to complete the questionnaire was 1.2 min. The internal consistency was 0.69 and 0.86 in cohorts 1 and 2 respectively. The test-retest correlation was 0.88. The GFS showed a high responsiveness to difference and change. The effect size was 0.82-0.96 in surgically treated disc herniation and 0.55-0.85 in spondylolisthesis. The GFS is a highly valid and reliable instrument with good responsiveness and feasibility, useful for evaluation of physical disability.

Validation of the Tunisian version of the Roland-Morris questionnaire

“…For illiterate patients, the questionnaire was administered by the observer. We also administered the General Function Score [9]. Patients were asked to attend an additional assessment 1 week later, at admission to the ward for local corticosteroid injections.…”

Randomized Clinical Trial of Lumbar Instrumented Fusion and Cognitive Intervention and Exercises in Patients with Chronic Low Back Pain and Disc Degeneration

“…A similar measurement error was reported in another study. 17 Secondary outcome measures were assessed in a standardized questionnaire, which was completed before inclusion and at the 1-year follow-up visit. Patients scored the intensity of their back and lower limb pain on vertical visual analogue scales, ranging from 0 to 100, wherein 100 reflected the worst pain imaginable.…”

“…The General Function Score was used to measure backrelated disability in activities of daily living. 17 Patients answered nine questions using one of the three alternatives: "can perform," "can perform with difficulty due to back complaints" and "cannot perform due to back complaints." The score was presented as a percentage wherein 100% represents maximum disability.…”

Pain-drawing does not predict the outcome of fusion surgery for chronic low-back pain: a report from the Swedish Lumbar Spine Study

“…Disability was measured with the Oswestry Disability Index (ODI) [11] and the General Function Score (GFS) [19]. Back pain was measured with the visual analogue scale (VAS).…”