Change in healthcare during Covid-19 pandemic was assessed through observational designs

Objective: Methodological challenges for investigating the changes in healthcare utilization during COVID-19 pandemic must be considered for obtaining unbiased estimates. Study design and setting: A population-based study in the Lombardy region (Italy) measured the association between the level of epidemic restrictions (increasing exposure during pre-epidemic, post-lockdown, and lockdown periods) and the recommended healthcare (outcome) for patients with schizophrenia, heart failure, chronic obstructive pulmonary disease, breast cancer, and pregnancy women. Two designs are applied: the self-controlled case series (SCCS) and the usual cohort design. Adjustments for between-patients unmeasured confounders and seasonality of medical services delivering were performed. Results: Compared with pre-epidemic, reductions in delivering recommended healthcare during lockdown up to 73% (95% confidence interval: 63%–80%) for timeliness of breast cancer surgery, and up to 20% (16%–23%) for appropriated gynecologic visit during pregnancy were obtained from SCCS and cohort design, respectively. Healthcare provision came back to pre-epidemic levels during the post-lockdown, with the exception of schizophrenic patients for whom the SCCS showed a reduction in continuity of care of 11% (11%–12%). Conclusion: Strategies for investigating the changes in healthcare utilization during pandemic must be implemented. Recommendations for taking into account sources of systematic uncertainty are discussed and illustrated by using motivating examples.