Cross-cultural comparison of the Scoliosis Research Society Outcomes Instrument between American and Japanese idiopathic scoliosis patients: are there differences?

Study Design: A comparative study.
Objective: To report a preliminary evaluation of the Scoliosis Research Society Outcomes Instrument (SRS-24) and determine whether differences in baseline scores exist between American and Japanese patients with idiopathic scoliosis.
Summary of Background Data: Because the SRS outcomes instrument was primarily introduced for the American population, baseline scores in the Japanese population might differ from the American population. A comparative study using the SRS instrument between American and Japanese patients with idiopathic scoliosis has not been reported.
Methods: Two comparable groups of 100 idiopathic scoliosis patients before spinal fusion were separated into American (A) and Japanese (J). There were no statistically significant differences between the groups for gender (A: 9 men/91 women vs. J: 13 men/87 women), age (A: 15.0 +/- 2.4 vs. J: 14.9 +/- 3.8), main curve location (A: 77 thoracic/23 lumbar, J: 76 thoracic/24 lumbar), main curve Cobb angle (A: 50.5 +/- 5.2 vs. J: 51.1 +/- 8.7), and thoracic kyphosis (A: 20.9 +/- 14.3 vs. J: 19.9 +/- 12.1) (P > 0.05, for all comparisons). Patients were evaluated using the first section of the SRS-24 which was divided into 4 domains: total pain, general self-image, general function, and activity. SRS-24 scores were statistical compared in individual domains and questions using the Mann-Whitney U test.
Results: American patients had significantly lower scores in pain (P < 0.0001, A: 3.7 +/- 0.8 vs. J: 4.3 +/- 0.4), function (P < 0.01, A: 3.9 +/- 0.6 vs. J: 4.2 +/- 0.5), and activity (P < 0.0001, A: 4.5 +/- 0.8 vs. J: 4.9 +/- 0.3) domains compared with Japanese patients. Japanese patients had significantly lower scores in the self-image (P < 0.0001, A: 4.0 +/- 0.7 vs. J: 3.5 +/- 0.5) domain. With regard to individual questions, there were significant differences in the scores between the 2 groups for all questions except 5 and 13 (P < 0.05, for all comparisons).
Conclusion: SRS-24 scores in the Japanese idiopathic scoliosis population differed from that of the American population. Japanese patients had less back pain, a negative self-image regarding back deformity, higher general physical function, and daily activity. It is highly probable that patient's perceptions differ due to cultural differences, which affect SRS-24 scores so a cross-cultural comparison of the SRS instrument content is necessary in the future.