A systematic review of empirical studies on methodology and burden of informal patient payments in health systems.

INTRODUCTION: Informal patients' payments (IPPs) is a sensitive subject. The aim of current study was to assess the trends in informal payment studies and explore methods of IPPs measurement, prevalence, and features (payment type, volume, and receiver) in various contexts.

METHODS: A search strategy was developed to identify peer-reviewed articles addressing informal payments on PubMed, Science Direct, Web of Science, Scopus, and CINAHL. A total of 1252 studies were identified initially. After screening process, 38 studies were included in the systematic review. The selected studies were appraised, and findings were synthesized.

RESULT: Among selected studies, quantitative approaches were mostly used for measuring IPPs from general public and patients' perspective, and qualitative methods mainly targeted health care providers. Reported IPP prevalence in selected articles ranges between 2% and 80%, more prevalent in the inpatient sector than in outpatient.

CONCLUSION: There are a number of strategies for the measurement of IPPs with different strengths and weaknesses. Most applied strategies for general public were quantitative surveys recruiting more than 1000 participants using a face-to-face structured interview, and then qualitative studies on less than 150 health care providers, with focus group discussion. This review provides a comprehensive picture of current informal patients' payments measurement tools, which helps researchers in future investigations.