Validity and Comparability of Out-of- pocket Health Expenditure from Household Surveys: A review of the literature and current survey instruments

Objective: Measurement errors have been a persistent concern in survey research. In this study we investigate the current evidence on measurement errors in self-reported household expenditure and health expenditure. Methodology: We performed a review of the literature on measurement error in healthcare-related surveys. A Pubmed-search was performed and in addition reference tracking was used. In the second part of the study we examined current survey instruments. We collected 90 household surveys, such as household budget surveys, from the International Household Survey Network. We included surveys that were conducted after 1990, with a focus on low-income countries and studied differences in survey design features. Results: The literature review demonstrated that the probability of misreporting increases when the time between interview and event increases. Also, longer and shorter recall periods have generated different outcomes, although the magnitude of this difference varied across populations. Furthermore, respondents reported higher aggregate household spending when more items were used. Respondents may also lose motivation in long-term diaries. Some studies found a relationship between measurement error and respondent characteristics, although results were inconsistent. The review of current household surveys showed a non-negligible variation in design features such as the recall period, the number of disaggregation items and the wording of questions. Conclusion: From reviewing the existing studies and literature we did not find evidence of the optimal survey design features in collecting data on health spending. However, some practical suggestions emerge from the study in terms of question design, recall period and methods of data collection. The study strongly suggests the need for validation studies in order to improve survey instruments and data quality. In the meantime, standardization could improve the comparability across countries and surveys, yet this may discourage the efforts on further exploring the best survey instruments and compromise within-country, overtime comparison efforts.