Case-case comparisons to study causation of common infectious diseases

Abstract

Case-case comparison is a development of case-control methodology made possible by laboratory typing techniques. These comparisons allow a more restricted but more refined analysis of the association of some exposures with infection. Determination of how exposure to the infectious agent occurred is more efficient and unbiased than in standard case-control studies but general factors determining whether disease occurs after an infectious exposure can not be studied.

Determining Risk Factors of a Non-Point Source Outbreak of Campylobacter Cases Using Case-Case and Case-Control Studies

“…However, this type of misclassification would bias the results towards the null because these cases would be more like the historical cases used as a comparison. Use of historical cases drawn from the same surveillance system as the outbreak cases reduces selection bias [35]. Recall bias is also minimized because all cases had symptoms and were interviewed within a similar time period following their laboratory confirmation.…”

“…While the spike in cases was noted in August (weeks [33][34][35][36], cases with onset dates from July -September were included as the outbreak cases to account for any earlier or later exposures or reporting. When the months of July (N=10), August (N=26) and September (N=12) were combined, a total of 48 suspect outbreak cases were included in the analyses.…”

Pigs as Source of Methicillin-ResistantStaphylococcus aureusCC398 Infections in Humans, Denmark

“…Furthermore, comparison of results from the case-control study (where farm/animal and medical-related variables remained associated) indicates that medical-related exposures are risk determinants for community-detected MRSA in general but not specifi cally for subtype CC398. This fi nding can be deduced because the design of the case-case analysis controls for exposures common to both groups, which means that these exposures will not be identifi ed as a risk or might be underestimated (20).…”

Epidemiologic Similarities in Pediatric Community-Associated Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus in the San Francisco Bay Area

“…We performed a prospective case-comparison investigation among pediatric patients from three medical centers in the San Francisco Bay Area [20]. For patients with a positive S aureus culture, we performed a chart review to evaluate clinical and demographic factors, telephoned parents or guardians of subjects to administer an extensive interview evaluating the 6 "Cs" of potential risk factors, and genotyped isolates for strain characterization.…”