Similar studies have been much smaller with marked selection bias, usually ascertaining only patients with non insulin-requiring diabetes (2– 9).
The gaps in Hess' memory are ascertained only on the basis of the subjective changing of his testimony about his inability to remember this or that person or event given at different times.
We could ascertain only whether the AEC service was available at the index hospital but not whether patients actually used the service.
Because exposure status at the time of blood draw might be most strongly correlated with estradiol, we also evaluated each of the variables at the time of blood draw or, for variables ascertained only on the main study questionnaire (for example, alcohol intake), within 2 years of blood draw.
Food consumption was ascertained only in the past 24 hours, and did not assess the quantity of food or frequency which foods were consumed by food group, in mothers and children, this may have blunted the ability to detect an association with stunting in our models, a challenge found in other investigations using survey data [ 34, 41].
Furthermore, this would not have biased the subgroup analysis that excluded early deaths, since deaths were ascertained only after the first year of follow-up for patients who both did and did not use the study drugs.
Women aged 20 79 years at breast cancer diagnosis were included unless they had previously been registered with a different cancer, their cancer was bilateral, of unknown laterality, metastatic, diagnosed at autopsy, or ascertained only from the death certificate.
In the United Kingdom, the NCAS ascertains only around 40% of the congenital anomalies compared with the BINOCAR registries (Boyd et al. 2005).
The follow-up for the patients who returned a non-zero score on the suicide-ideation item was ascertained only by interviewing the practice nurses concerned to maintain patient confidentiality.
