Full Answer Section

• diagnostic process confirming monkeypox via PCR, the specific ophthalmological findings, the treatment provided (supportive care, topical antibiotics), and the patient’s eventual recovery. The purpose was to alert clinicians to potential eye involvement in monkeypox infections, which might otherwise be overlooked. It serves as an early observation and potential hypothesis generator regarding the virus’s tropism or secondary effects.

2. Case Series

• Definition: A case series expands on the case report by describing characteristics of a group of individuals who share a similar diagnosis, exposure, or outcome. There is typically no pre-planned comparison group (Aschengrau & Seage, 2020). Case series are useful for describing the spectrum of a disease, identifying common features among affected individuals, or documenting early trends, especially for emerging conditions. Like case reports, they are primarily descriptive and cannot definitively prove causation.

• Example Article: Dufort, E. M., Koumans, E. H., Chow, E. J., Rosenthal, E. M., Muse, A., Rowlands, J., Barranco, M. A., Maxted, A. M., Rosenberg, E. S., Easton, D., Udo, T., Kumar, J., Pulver, W., Smith, L., Hutton, B., Blog, D., & Zucker, H. (2020). Multisystem inflammatory syndrome in children in New York State. New England Journal of Medicine, 383(4), 347-358. https://doi.org/10.1056/NEJMoa2021756

• Description: This article examines a cluster of children and adolescents in New York State who presented with severe inflammatory illness following exposure to SARS-CoV-2. The defining characteristic making this a case series is the aggregation and description of multiple patients (99 initially identified meeting the case definition) sharing a specific, novel clinical syndrome (Multisystem Inflammatory Syndrome in Children, or MIS-C). The authors collected and analyzed data on the demographic characteristics, clinical signs and symptoms (e.g., fever, rash, cardiac dysfunction), laboratory findings (e.g., elevated inflammatory markers), treatments administered (e.g., intravenous immunoglobulin, steroids), and outcomes (e.g., ICU admission, mortality) for this group. The study describes the shared features of this emerging syndrome, providing a clearer picture of its presentation and severity than a single case report could. It highlights the temporal association with COVID-19 but, lacking a formal comparison group, primarily serves to characterize the syndrome and raise awareness.

3. Cross-Sectional Study

• Definition: A cross-sectional study examines the relationship between diseases (or other health-related characteristics) and other variables of interest as they exist in a defined population at one particular point in time (Celentano & Szklo, 2019). Exposure and outcome are assessed simultaneously. These studies are often called “prevalence studies” because they provide a snapshot of the frequency and distribution of health states or factors in a population. They are useful for assessing the burden of disease, evaluating diagnostic tests, and exploring associations, but they cannot establish the temporal sequence between exposure and outcome (i.e., did the exposure precede the outcome?).

• Example Article: Exelmans, L., & Van den Bulck, J. (2016). Bedtime mobile phone use and sleep in adults. Social Science & Medicine, 148, 93-101. https://doi.org/10.1016/j.socscimed.2015.11.037

• Description: This study investigated the association between using a mobile phone at bedtime and sleep outcomes in a sample of adults. The defining characteristic making this a cross-sectional study is that both the exposure (frequency and type of mobile phone use in bed after lights out) and the outcomes (sleep duration, sleep quality, fatigue, sleep latency) were measured concurrently using surveys administered at a single time point. The researchers recruited a large sample of adults and asked them about their current phone habits and recent sleep experiences. They then analyzed the data to see if higher levels of bedtime phone use were associated with poorer sleep outcomes within that snapshot in time. The study found a significant association, suggesting that bedtime phone use might negatively impact sleep. However, because data were collected simultaneously, it cannot definitively prove that phone use caused poor sleep; it’s possible that people with poor sleep are more likely to use their phones in bed (reverse causality) or that another factor influences both. It provides valuable information on the prevalence of the behavior and its association with sleep issues in the studied population.

In summary, these three study designs represent different approaches along a spectrum of epidemiological investigation. Case reports and series are often initial steps, providing detailed descriptions of novel or unusual occurrences in individuals or small groups, crucial for hypothesis generation. Cross-sectional studies offer a snapshot of a population at a single point in time, useful for measuring prevalence and identifying associations, but limited in determining cause-and-effect relationships (Celentano & Szklo, 2019; Aschengrau & Seage, 2020). Each design contributes uniquely to our understanding of health and disease patterns.