2.2 Case Series
The majority of the remaining studies present case series. They present similar cross-sectional evidence to the questionnaire designed studies with a common aim of investigating the symptomology of anosmia in the COVID-19 era. This approach should contribute to limiting the level of bias in their results when compared to an outcome-based case series but they are similarly only able to demonstrate association and not causal effect. The complementary data output, between the questionnaire and case-series approaches, allows us to compare the two approaches concurrently in a meta-analysis.