Information on fatal PCa cases was ascertained through linkage to the Swedish Register of Death Causes at the National Board of Health and Welfare.
A cohort of diagnosed diabetes cases was ascertained from physician claims, insured resident registry and hospitalisation records.
Information on hormone replacement therapy (HRT) use and tumor characteristics in sporadic breast cancer cases was ascertained from a postal questionnaire and pathology reports, respectively.
The study size was determined based on a priori sample size calculations, and cases were ascertained from provincial cancer registries, except in Quebec where hospital ascertainment was used.
The CHD cases were ascertained using an annual follow-up questionnaire and validated by an End Point Committee through a review of the medical records.
Whether the pollution originates mainly from an outside source, or it is derived from indoor sources, or even from the object itself, can in most cases be ascertained by the method.
For example, in most vaccine field trials, cases are ascertained based on clinical symptoms, then the specific infectious agent is confirmed by a laboratory test, so efficacy against clinical disease is determined.
Among them, 57 incident GDM cases were ascertained and 114 women who were not diagnosed with GDM were selected as controls.
While cases were ascertained from passive reporting by clinicians, who may have underreported cases due to under-recognition or limited access to confirmatory laboratory testing, these limitations are unlikely to have introduced any selection bias that would affect these findings.
A survey in New York City, where case ascertainment was aggressive surrounding the St. Francis School outbreak, indicated that over 1000 persons associated with the school experienced influenza-like illness, in a period where only 74 confirmed or probable cases were ascertained.
