Confirmatory factor analysis and recommendations for improvement of the Autonomy-Preference-Index (API)

• Published in: Health expectations : an international journal of public participation in health care and health policy 2010-09, Vol.13 (3), p.234-243
• Main Authors: Simon, Daniela, Kriston, Levente, Loh, Andreas, Spies, Claudia, Scheibler, Fueloep, Wills, Celia, Härter, Martin
• Format: Article
• Language: English
• Subjects: Adult; Age Factors; Aged; Arthritis; Assessing Involvement and Decision‐making; Autonomy; Chronic illnesses; Computation; Confirmatory factor analysis; Decision Making; Discriminant analysis; Emergency medical care; Emergency medical services; Emergency Service, Hospital - statistics & numerical data; Emergency services; Factor analysis; Female; German language; Health Care Surveys - statistics & numerical data; Humans; Information seeking; Information seeking behavior; Inpatient care; Inpatients - psychology; Internal medicine; Male; measurement; Medicine; Middle Aged; Modification; Outpatients - psychology; Patient education; Patient Participation; Patient Preference; patient preferences; Preferences; Primary care; Reliability; Sex Factors; Structural equation modeling; Subgroups; Surveys and Questionnaires; Validation; validation study
• ISSN: 1369-6513; 1369-7625
• DOI: 10.1111/j.1369-7625.2009.00584.x

Objective  Validation of the German version of the Autonomy‐Preference‐Index (API), a measure of patients’ preferences for decision making and information seeking. Methods  Stepwise confirmatory factor analysis was conducted on a sample of patients (n = 1592) treated in primary care for depression (n = 186), surgical and internal medicine inpatients (n = 811) and patients with minor trauma treated in an emergency department (n = 595). An initial test of the model was done on calculation and validation halves of the sample. Both local and global indexes‐of‐fit suggested modifications to the scale. The scale was modified and re‐tested in the calculation sample and confirmed in the validation sample. Subgroup analyses for age, gender and type of treatment setting were also performed. Results  The confirmatory analysis led to a modified version of the API with better local and global indexes‐of‐fit for samples of German‐speaking patients. Two items of the sub‐scale, ‘preference for decision‐making’, and one item of the sub‐scale, ‘preference for information seeking’, showed very low reliability scores and were deleted. Thus, several global indexes‐of‐fit clearly improved significantly. The modified scale was confirmed on the validation sample with acceptable to good indices of fit. Results of subgroup analyses indicated that no adaptations were necessary. Discussion and conclusions  This first confirmatory analysis for a German‐speaking population showed that the API was improved by the removal of several items. There were theoretically plausible explanations for this improvement suggesting that the modifications might also be appropriate in English and other language versions.