A co- prevalent case was defined as someone who was diagnosed with TB within two months after enrollment of the index case [14].
From our database, we identified as household case-patients their household members for whom TB was diagnosed within 24 months after enrollment of the index case-patient.
Also, the legislation mandates a review of regulatory requirements for clinical trial data, to take into account the limited number of patients available for enrollment in the case of more rare pathogens [ 5, 13].
The major strengths of the present study are the enrollment of incident cases and randomly sampled population controls; the large sample size; the unusually high participation rates, especially considering that biologic samples were requested; and the face-to-face collection of detailed information with a structured questionnaire by trained interviewers.
The controls had a similar distribution across time of enrollment as the cases.
At each GEMS study site, children 0 59 months of age who had MSD and were brought to one of the site's SHCs were enrolled into the study, along with 1 or more controls who were matched to the case by age, time (within 7 days of the case enrollment), and geographic location of residence.
The distribution of ages and year of enrollment of the final sample of 12,093 cases and 122,411 controls is shown in Table 1.
For study hospitals that did not have a central review committee, we followed two procedures: (1) we identified study collaborators who were available in the clinics for enrollment of IBC cases and (2) we asked study collaborators to notify clinic physicians who were not collaborators to refer IBC cases to study collaborators.
Sensitivity is determined largely by the placement of the surveillance system within the healthcare system and the completeness of enrollment of case-patients.
Because in most sites the incidence of pneumonia is highly seasonal and the pathogens that cause pneumonia are also seasonal, we debated whether to match controls to the dates of enrollment of cases or to recruit controls at a constant rate throughout the year.
