Calibration of an item bank in 474 orthopedic patients using Rasch analysis for computer-adaptive assessment of anxiety.

OBJECTIVE

To calibrate an item bank of anxiety-related questions for use in orthopedic patients within a computer-adaptive test.

DESIGN

This is a psychometric study.

SETTING

The sample of orthopedic patients was recruited in two orthopedic rehabilitation clinics in Germany.

SUBJECTS

A total of 474 orthopedic rehabilitation patients were recruited for this study.

INTERVENTIONS

Not applicable.

MAIN MEASURES

The main measure is an adapted version of an existing anxiety item pool for cardiovascular rehabilitation patients.

RESULTS

The results of the confirmatory factor analysis and Mokken analysis confirmed a one-factor structure and double monotonicity. An anxiety item bank (48 items) could be developed and calibrated using Rasch analysis. It fitted to the Rasch model with a non-significant item-trait interaction ((203) = 172.59;  = .94) and was free of differential item functioning. Unidimensionality could be verified and the person separation reliability was .96. The category threshold parameters varied between 4.72 and 3.16 (7.88 logits).

CONCLUSION

The unidimensional anxiety item bank provides the basis for a computer-adaptive test to assess a wide range of anxiety in rehabilitation patients with orthopedic diseases with very good psychometric characteristics.