Development and Validation of an Instrument to Measure Health-Related Out-of-Pocket Costs: The Cost for Patients Questionnaire

Abstract

Objective: The growth of healthcare spending is a major concern for insurers and governments but also for patients whose health problems may result in costs going beyond direct medical costs. To develop a comprehensive tool to measure direct and indirect costs of a health condition for patients and their families to various outpatient contexts.

Methods: We conducted a content and face validation including results of a systematic review to identify the items related to direct and indirect costs for patients or their families and an online Delphi to determine the cost items to retain. We conducted a pilot test-retest with 18 naive participants and analyzed data calculating intraclass correlation and kappa coefficients.

Results: An initial list of 34 items was established from the systematic review. Each round of the Delphi panel incorporated feedback from the previous round until a strong consensus was achieved. After 4 rounds of the Delphi to reach consensus on items to be included and wording, the questionnaire had a total of 32 cost items. For the test-retest, kappa coefficients ranged from -0.11 to 1.00 (median = 0.86), and intraclass correlation ranged from -0.02 to 0.99 (median = 0.62).

Conclusions: A rigorous process of content and face development was implemented for the Cost for Patients Questionnaire, and this study allowed to set a list of cost elements to be considered from the patient's perspective. Additional research including a test-retest with a larger sample will be part of a subsequent validation strategy.

Keywords: Delphi process; cost measurement; patient perspective; questionnaire development; questionnaire validation; test-retest.