Developing a Functional Staging to Assist Clinical
Interpretation of the Oswestry Disability Index

Ying-Chih Wang; Jay Kapellusch; Bhagwant Sindhu; Leigh Lehman; Xiaoyan Li; Sheng-Che Yen

doi:10.26717/BJSTR.2018.12.002200

Research ArticleOpen Access

Developing a Functional Staging to Assist Clinical Interpretation of the Oswestry Disability Index

Volume 12 - Issue 1

**Ying-Chih Wang*¹, Jay Kapellusch¹, Bhagwant Sindhu¹, Leigh Lehman², Xiaoyan Li³ and Sheng-Che Yen⁴**

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- ¹Department of Occupational Science & Technology, USA
- ²Department of Occupational Therapy, USA
- ³Department of Physical Medicine and Rehabilitation, USA
- ³Department of Physical Therapy, USA

Received: December 06, 2018; Published: December 13, 2018

DOI: 10.26717/BJSTR.2018.12.002200

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Abstract

Objective: Our purposes were to: (a) examine the psychometric properties of 10-item Oswestry Disability Index 2.0 (ODI) (0-100) questionnaire using the Rasch analysis, and (b) develop a functional staging approach to guide clinical interpretation of the patient’s improvement by interpreting ODI scores.

Participants. A sample of 3,460 patients with orthopedic lumbar spine impairments seeking outpatient physical therapy in 274 clinics.

Methods: We examined the rating scale structure, item difficulty hierarchy, item fit, person-item match, separation index, differential item functioning (DIF) by demographic variables, and unidimensionality. Additionally, applied the keyform method to develop a functional staging.

Results: The ODI questionnaire has sufficient psychometric properties. ‘Lifting’ appeared to be the most difficult item. ‘Personal care” was the easiest. The coverage of ODI items matched well with the patient functional abilities. With a separation index equaled to 2.15, the ODI items can differentiate persons into 3.2 statistically distinct person strata. ODI items were free of DIF by gender and impairment, but four to five items were suggestive of DIF by age group and symptom acuity. Factor analysis supported one-factor solution; however, the first factor explained only 49.6% of the total variance. We provided an example of functional staging application.

Conclusion: Results supported the clinical usage of the ODI questionnaire in outpatient (orthopedic) rehabilitation service.

Keywords :Rasch Analysis; Lumbar Spine; Outpatient Rehabilitation; Low Back Pain; Psychometrics

Abbreviations : ODI: Oswestry Disability Index; ICC: Intraclass Correlation Coefficient; DIF: Differential Item Functioning