25 Routine surveillance is usually too insensitive to assess accurately any changes in the prevalence or incidence of VL, 15, 27 with most case detection being passive.
The linked data also allowed assessment of trends in hospitalisation independent of trends in CAP incidence, with detailed adjustment to account for any changes in the prevalence of patient risk factors for hospitalisation over time.
To examine whether there was a change in the prevalence in any of the 3 most abundant subgenotypes (4a, 4c, and 4d) detected, we conducted χ analyses.
This alteration represents a change in the prevalence by gender of treated stone disease from a 1.7:1 to 1.3 1 male-to-female ratio.
Also, the Norwegian HUNT 2 and HUNT 3 studies do not show any change in the one-year prevalence rates within eleven years [9, 28].
Any future change in the prevalence of these diseases will therefore result in changing health care needs, not only within hospitals but also in terms of providing long-term care after discharge.
As the prevalence and incidence figures for this study relate to diagnosed ADHD, it is possible that any change in incidence or prevalence rates during the study period is an ascertainment effect.
We did not find any change in CHD prevalences, in line with the trends observed in some parts of Europe, where after an increase in the early 1990s due to improvements in echocardiographic investigations, rates have remained stable.
Results from the largest epidemiologic study of changes in prevalence and treatment of mental disorders, the US based National Comorbidity Survey [ 11], does not suggest any change in prevalence from 1990 to 2003.
To determine if, and why, any changes in HIV prevalence had occurred during the early to mid 1990s, further studies were conducted.
