Pattern of OPD utilisation during the COVID-19 pandemic under the Universal Coverage Scheme in Thailand: what can 850 million records tell us?

BACKGROUND: Out-patient department (OPD) is a crucial component of the healthcare systems in low- and middle-income countries including Thailand. A considerable impact of coronavirus disease 2019 (COVID-19) pandemic and its control measures, especially the lockdown, on utilisation of OPD services was expected. This study thus aims to estimate the pattern of OPD utilisation during the COVID-19 pandemic in Thailand including overall utilisation and within each sub-groups including diagnostic group, age group, and health region. METHODS: This study was a secondary data analysis of aggregated outpatient data from patients covered under the Universal Coverage Scheme (UCS) in Thailand over a 4-year period (2017–2020). Interrupted time series analyses and segmented Quasi-Poisson regression were used to examine the impact of COVID-19 on the overall OPD utilisation including the impact on each diagnostic group, age groups, health regions, and provinces. RESULTS: Analysis of 845,344,946 OPD visits in this study showed a seasonal pattern and increasing trend in monthly OPD visits before the COVID-19 pandemic. A 28% (rate ratio (RR) 0.718, 95% confidence interval (CI): 0.631–0.819) and 11% (RR 0.890, 95% CI: 0.811–0.977) reduction in OPD visits was observed during the lockdown and post-lockdown periods, respectively, when compared to the pre-lockdown period. Diseases of respiratory system were most affected with a RR of 0.411 (95% CI: 0.320–0.527), while the number of visits for non-communicable diseases (ICD-10: E00–E90, I00–I99) and elderly (> 60 years) dropped slightly. The post-lockdown trend in monthly OPD visits gradually increased to the pre-pandemic levels in most groups. CONCLUSIONS: Thailand’s OPD utilisation rate during the COVID-19 lockdown decreased in some diseases, but the service for certain group of patients appeared to remain available. After the COVID-19 lockdown, the rate returned to the pre-pandemic level in a timely manner. Equipped with a knowledge of OPD utilisation pattern during COVID-19 based on a national real-world database could aid with a better preparation of healthcare system for future pandemics. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12913-023-09121-3.