Through these rigorous techniques we are confident in achieving a high case ascertainment level.
For the age-group >15 years in Sweden, as in other countries (22), the ascertainment level is lower because of the more complicated and varied routines for care of newly diagnosed patients.
Using a computer-based patient administrative register as a secondary source, the level of ascertainment of type 1 diabetes during 1983 1987 was estimated as 91% in Västerbotten County in northern Sweden, covering 2.9% of the population, with no trend in ascertainment level during 1986–1997.
The difference in size of the ORs may be due to variation in age, outcome ascertainment, level of infection (e.g. the prevalence of H. pylori in these studies was < 10% [ 5, 6] compared with > 40% in ours), and differences in measurement of infection status (serology vs. rapid stool antigen test used in the current study).
Biased pyramidal sCFR estimates can also result from reporting biases and inconsistent case ascertainment between surveillance levels.
For Campylobacter enteritis, for which a reliable estimate of community incidence exists, we corrected for this by accounting for the magnitude and variability of ascertainment at clinic level, the factor most likely to influence ascertainment.
First that the level of unlinked deaths was so low that results could hardly been affected when including them, or second that the unlinked deaths did not importantly change sensitivity and specificity of mortality ascertainment by educational level.
However, studies have shown that even highly experienced clinicians have low reliability in accurate ascertainment of spinal level, suggesting that measurement strategies based on palpation have inherent limitations [ 32].
Conclusions: Variations in maternal mortality ratios reflect different data sources with varying levels of ascertainment in addition to differences in the number of maternal deaths.
