Hidden out-of-pocket spending on health: A cross-sectional study on underestimation of catastrophic health spending in Vietnam.

Objectives: To assess the extent to which excluding indirect out-of-pocket (OOP) spending leads to an underestimation of the incidence of catastrophic health spending (CHS) in Vietnam, where family members are responsible for essential in-hospital care, resulting in substantial indirect OOP spending. Study design: A cross-sectional retrospective facility-based survey. Methods: A total of 219 households with inpatient or outpatient members at Phu Tho Provincial General Hospital were interviewed using a structured questionnaire, to collect data on direct and indirect OOP spending and socioeconomic characteristics. Direct OOP spending was extracted from hospital billing records. The incidence of CHS was calculated using three thresholds: (i) spending >40% of non-food household expenditure (CHS40); (ii) spending >25% of total household expenditure (CHS25); and (iii) spending >10% of total household expenditure (CHS10). Results: Inclusion of indirect OOP spending significantly increased the incidence of CHS across the three thresholds. At the CHS40 threshold, the incidence increased from 15.1% (based on direct OOP spending only) to 31.1% after incorporating indirect OOP spending, a 2.06-fold increase. Similar trends were confirmed under the CHS25 and CHS10 thresholds. Key contributors to indirect OOP spending included health insurance premiums, meals for patients and caregivers, and transportation. Notably, 16.0% of households were categorized as experiencing CHS40 only when indirect spending was incorporated. These results highlight a substantial underestimation of financial burden under the current WHO and World Bank definition of OOP spending, which excludes indirect OOP spending. Conclusions: Excluding indirect OOP spending significantly underestimates the true incidence of CHS in Vietnam. Revising global definitions of OOP spending to include indirect OOP components may need to be considered to improve the accuracy of monitoring of financial protection. In the Vietnamese context, increasing the nurse-to-doctor ratio may help reduce indirect OOP spending and thereby the incidence of CHS. Further population-based research is needed.