[Examination of calibrated item banks for the assessment of work capacity in an outpatient sample of cardiological patients]

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 (χ²(203) = 172.59; P = .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.

Development and calibration of an item bank for the assessment of activities of daily living in cardiovascular patients using Rasch analysis

Background

To develop and calibrate the activities of daily living item bank (ADLib-cardio) as a prerequisite for a Computer-adaptive test (CAT) for the assessment of ADL in patients with cardiovascular diseases (CVD).

Methods

After pre-testing for relevance and comprehension a pool of 181 ADL items were answered on a five-point Likert scale by 720 CVD patients, who were recruited in fourteen German cardiac rehabilitation centers. To verify that the relationship between the items is due to one factor, a confirmatory factor analysis (CFA) was conducted. A Mokken analysis was computed to examine the double monotonicity (i.e. every item generates an equivalent order of person traits, and every person generates an equivalent order of item difficulties). Finally, a Rasch analysis based on the partial credit model was conducted to test for unidimensionality and to calibrate the item bank.

Results

Results of CFA and Mokken analysis confirmed a one factor structure and double monotonicity. In Rasch analysis, merging response categories and removing items with misfit, differential item functioning or local response dependency reduced the ADLib-cardio to 33 items. The ADLib-cardio fitted to the Rasch model with a nonsignificant item-trait interaction (chi-square=105.42, df=99; p=0.31). Person-separation reliability was 0.81 and unidimensionality could be verified.

Conclusions

The ADLib-cardio is the first calibrated, unidimensional item bank that allows for the assessment of ADL in rehabilitation patients with CVD. As such, it provides the basis for the development of a CAT for the assessment of ADL in patients with cardiovascular diseases. Calibrating the ADLib-cardio in other than rehabilitation cardiovascular patient settings would further increase its generalizability.