The phrase "ascertained largely through" is correct and usable in written English.
It can be used when discussing how information or conclusions have been determined or discovered, emphasizing the primary methods or sources involved.
Example: "The results of the study were ascertained largely through extensive surveys and interviews with participants."
Alternatives: "determined mainly by" or "established primarily through".
During the same period, suspect cases of swine flu were being ascertained largely through patients or concerned persons responding to media interest and contacting their general practitioners or through the active follow-up by public health services of contacts of confirmed or suspect cases, often where local school outbreaks had been recognised.
COPD and comorbid disease status were ascertained largely through NHANES questions asking "has a doctor or other health professional ever told you that you have [disease]?" Physician-diagnosed COPD was defined as a positive response to either chronic bronchitis or emphysema with a negative response to current asthma.
The number of individuals in solitary confinement/administrative segregation at any given time is not easily ascertained, largely because of the variance in record keeping and reporting among the U.S.'s city, state, and federal prisons, detention facilities, and jails.
Falls were ascertained prospectively through the facilities' computerized incident reports.
Therefore, the bias caused by the classification scheme could be largely ameliorated and the diagnostic potential of the features could be ascertained through extensive experiments.
Their molecular structures were further ascertained through single crystal X-ray diffraction studies.
Their structure are established and ascertained through spectral and single crystal XRD studies.
Gene level, as well as genomic level of DNA methylation, is ascertained through this technique.
Community opinions of the trial were ascertained through 10 focus groups.
Outbreaks of gastroenteritis were ascertained through an active surveillance network using standard clinical definitions.
