A New Objective Health Numeracy Test for Patients with Type 2 Diabetes: Development and Evaluation of Psychometric Properties

Psychometric evaluation of the Korean version of PROMIS self-efficacy for managing symptoms item bank: Item response theory

PURPOSE

To evaluate the psychometric properties of the Patient-Reported Outcomes Measurement Information System (PROMIS) self-efficacy for managing symptoms of the version 1.0 item bank in Korean.

METHODS

This study consisted of two phases: first, developing the Korean version of the item bank following the translation guidelines; and second, performing a cross-sectional study to evaluate its psychometric properties using the item response theory. This study enrolled 323 patients with type 2 diabetes mellitus between July and August 2020. Cronbach's α was used to assess the reliability of this item bank. Confirmatory factor analysis, using diagonally weighted least squares, was used to identify the assumptions of item response theory. Item parameter estimates including discrimination and thresholds were derived using the graded response model of the item response theory to reflect patient-reported outcomes as individualized responses.

RESULTS

The Korean version of the item bank demonstrated good reliability (Cronbach's α =.98) and its discrimination ranged from 1.82 to 4.93. The thresholds resulted in the establishment of a category response curve for each item. However, no overlap was observed among the category curves. Moreover, the differential item functioning was not significant for age, gender, and income variables.

CONCLUSION

The graded response model and differential item functioning provided qualitative evidence that demonstrated acceptable psychometric properties of symptom management self-efficacy among patients. This item bank is expected to provide adequate assessments of self-efficacy of symptom management for patients with a chronic disease, which can contribute to nursing research and intervention.

Psychometric properties of the revised Diabetes Knowledge Test using Rasch analysis

OBJECTIVE

The revised Diabetes Knowledge Test (DKT2) is the instrument that is the most widely used for measuring diabetes knowledge; nevertheless, its structural validity has never been evaluated. This study aimed to determine the psychometric properties of the DKT2.

METHODS

This study performed a secondary data analysis of people with diabetes recruited at university hospitals. Rasch analysis was used.

RESULTS

One item in the 14-item DKT2 measuring general diabetes knowledge exhibited a poor-fit, and so it was eliminated. The person-item map showed that items of greater difficulty need to be added to the instrument. The principal-components analysis of residuals revealed a unidimensional structure. The person reliability was 0.50, with a person separation index of 1.01. Measurement invariance was not satisfied for items 11 and 2 according to gender and age.

CONCLUSIONS

The unidimensional structure of the 13-item DKT2 demonstrated poor person reliability and a low person separation index. Females and elderly persons found it more difficult to respond to items 11 and 2, respectively.

PRACTICE IMPLICATIONS

Careful consideration is necessary when using the 13-item DKT2 in practice and research. It is recommended for future studies to add items of greater difficulty to the instrument.