The aim of the present study was to compare measurement precisions of the Oswestry Back Pain Disability Questionnaire (ODQ) and a computer adaptive testing (CAT) method. The ODQ has been regarded as one of the most reliable condition-specific measure for back pain for decades. Cross-sectional study was carried out with two independent convenient samples from two out-patient rehabilitation clinics for back pain (n1=42) and non-back pain group (n2=42). Participants were asked to fill out the ODQ and CAT of International Classification of Functioning, Disability and Health-Activity Measure (ICF-AM). A series of Rasch analyses were performed to calculate person ability measures. The CAT measures had greater relative precision in discriminating the groups than did the ODQ measure in comparisons of the relative precision. The CAT measure appears to be more effective than did the ODQ measure in terms of measurement precision. By administering test items calibrated in a way, CAT measures using item response theory may promise a means with measurement precision as well as efficiency.

Three hundred and fourteen low back pain patients completed the Korean version of the Oswestry Disability Questionnaire (KODQ) and the Rasch analysis was then applied to identify the inappropriate items and to determine ODQ item difficulties according to a subject's characteristics. For women and youths, the 'sex life' item showed misfit statistics, whereas for older subjects it was the 'pain intensity' and 'standing' items. Also, in the acute low back group the 'pain intensity', 'standing' and 'sex life' items showed misfit statistics. For all subjects, the most difficult item was 'pain intensity', whereas the easiest item was 'walking'. But for the older and acute groups 'lifting' was the most difficult item and for those who have a visual analogue scale score of 3 or less 'sitting' was the most difficult item. These results show that differential item functioning is present in several items according to sex, age, acute and chronic pain, and VAS score. This study may be useful for adjusting the KODQ item difficulties for low back pain patients with different characteristics

The purposes of this study were to assess and modify the original classification categories of the modified Oswestry Low Back Pain Disability Questionnaire (ODQ) and to determine the unidimensionality of the modified ODQ applying Rasch Analysis. The data were obtained from 108 work-related low back pain patients by physical therapists. Construct validity of the scale using the Rasch model required the structure of the rating scale to be modified from 6 response levels to 4 response levels. Eight items from the modified ODQ fit the Rasch model. The items, "pain intensity" and "social life" showed misfit statistics. In general, the order of item difficulty of the remaining 8 items showed a logical item difficulty hierarchy with the "changing degree of pain" item being the most difficult and the "walk" item being the easiest. The results showed that further study is needed to expand the construct of ODQ including additional higher-level items related to work activities. This study may be useful for establishing a standard method to assess the functionality of low back pain patients.