A case report is the description of the clinical story of a single patient. A cross-sectional study involves a group of participants on which data is collected at a single point in time to investigate the relationship between a certain exposure and an outcome.
Here’s a table that summarizes the relationship between a case report and a cross-sectional study:
| Case Report | Cross-Sectional Study | |
|---|---|---|
| Participants involved | A case report describes the medical case of 1 particular patient | A cross-sectional study is a snapshot in time of a sample of participants chosen from the population |
| Goal | To report an interesting or unusual case of a patient | To describe the association between an exposure and an outcome |
| Study type | Observational (because the researcher only observes and describes the patient’s case and does not manipulate or control the events) | Observational (because the researcher does not influence who gets the exposure and who doesn’t) |
| Follow-up over time | Yes, sometimes the case report involves following the patient over a period of time | No, in a cross-sectional study the exposure and the outcome are measured simultaneously and so there is no need to follow participants over time |
| Example | In 1991, Fred Kern, Jr. reported the case of an 88-year-old man who has been eating 20-30 eggs each day for almost 15 years. The man had a normal cholesterol level as his body adapted to his unusual diet. [Source] | In 1999, Von Kries et al. measured, at the time of school entry, the weight of children and whether or not they had been breastfed and for how long. The study concluded that prolonged breastfeeding (the exposure) may decrease the prevalence of childhood obesity (the outcome). [Source] |
| Advantages | Simple and inexpensive: as it involves following 1 patient only | – Fast to conduct: because participants are not followed over time – Useful for assessing the disease burden in the population |
| Limitations | Is considered a weak design because: – It represents a single story that does not always generalize to other cases. – Conclusions based on case reports may be biased (because the observed patient is not chosen at random from the population) or confounded by some unmeasured factors. | Is a weak design for assessing a causal relationship between exposure and outcome because of: – Reverse causality: As the exposure and the outcome are measured at the same time, it is hard to determine which came first. – Survival bias: The study may be excluding those who died from the exposure (especially those who died after being exposed but before the study was carried out), therefore the results may be biased towards concluding that the exposure is less harmful than it really is. |
| Level of evidence | Has the lowest level of evidence of all study designs | Is one step better than the case report |