Case-Crossover Clinical Study

A Case-Crossover Clinical Study is an Observational Clinical Study that relies upon a patient to act as their own control group as for minimizing potential confounder.

• Context:
  • It can be a retrospective study or prospective study in which the disease risk measures is odds ratio.
  • Strengths/Advantages:
    • Reduces some types of bias;
    • Good for acute health outcomes with a defined disease exposure;
    • Cases act as their own control group.
  • Weaknesses/Disadvantages:
    • selection of comparison time point difficult;
    • challenging to execute;
    • prone to recall bias;
    • No demonstrated temporality.
• Example(s):
  • an observational clinical study that evaluates the exposure of a driver (case) talking on a cell phone and being involved in an automobile crash.
  • NCT04743323: A Case-CrossovEr Study deSign to Inform Tailored Interventions to Prevent Disease (ACCESS-AP),
  • NCT00759174: Case Crossover Study of PDE5 Inhibitor Exposure as a Potential "Trigger Factor" for Acute NAION,
  • NCT05111873: Effects of Multimodal Treatment of Headache in a Day Clinic Service: a Prospective Case-crossover Study,
  • …
• Counter-Example(s):
  • Case-Control Clinical Study,
  • Cohort Clinical Study,
  • Cross-Sectional Clinical Study,
  • Ecological Clinical Study,
  • Proportional Mortality Ratio (PMR) Clinical Study.
• See: Disease Exposure Measure, Health Outcome Measure, Descriptive Clinical Trial, Diagnostic Clinical Trial, Interventional Clinical Trial, Uncontrolled Clinical Intervention Study.

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References

2022

• (ClinicalTrials.gov, 2022) ⇒ https://clinicaltrials.gov/ct2/about-studies/glossary Retrieved:2022-02-13.
  • QUOTE: Observational study model: The general design of the strategy for identifying and following up with participants during an observational study. Types of observational study models include cohort, case-control, case-only, case-cross-over, ecologic or community studies, family-based, and other.

2016

• (Grant, 2016) ⇒ William B. Grant (2016). "The role of geographical ecological studies in identifying diseases linked to UVB exposure and/or vitamin D". In: Dermato Endocrinology 8(1):e1137400. DOI:10.1080/19381980.2015.1137400.
  • QUOTE: Observational studies come in several forms:
    • Case–control. Risk-modifying factors measured at the time of disease diagnosis.
    • Cohort and nested case–control. Subjects are enrolled in a study, risk-modifying factors are assessed, and then the cohort is monitored (for up to many years). Those who develop diseases are compared with like individuals who did not.
    • Cross-sectional. An entire population is sampled, with health status and health parameters and risk-modifying factors measured.

2014

• (Thiese, 2014) ⇒ Matthew S. Thiese. (2014). “Observational and Interventional Study Design Types; An Overview.” In: Biochemia Medica (Zagreb). Journal, 24(2).
  • QUOTE: A case-crossover study relies upon an individual to act as their own control for comparison issues, thereby minimizing some potential confounders (...). This study design should not be confused with a crossover study design which is an interventional study type and is described below. For case-crossover studies, cases are assessed for their exposure status immediately prior to the time they became a case, and then compared to their own exposure at a prior point where they didn’t become a case. The selection of the prior point for comparison issues is often chosen at random or relies upon a mean measure of exposure over time. Case-crossover studies are always retrospective. An example of a case-crossover study would be evaluating the exposure of talking on a cell phone and being involved in an automobile crash. Cases are drivers involved in a crash and the comparison is that same driver at a random timeframe where they were not involved in a crash. These types of studies are particularly good for exposure-outcome relationships where the outcome is acute and well defined, e.g. electrocutions, lacerations, automobile crashes, etc. (...). Exposure-outcome relationships that are assessed using case-crossover designs should have health outcomes that do not have a subclinical or undiagnosed period prior to becoming a “case” in the study (...). The exposure is cell phone use during the exposure periods, both before the crash and during the control period. Additionally, the reliance upon prior exposure time requires that the exposure not have an additive or cumulative effect over time (....). Case-crossover study designs are at higher risk for having recall bias as compared with other study designs (...). Study participants are more likely to remember an exposure prior to becoming a case, as compared to not becoming a case.

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