Definition and methods
‘Prevalence’ expresses the proportion of a defined population with a specific health problem in a defined period of time. FaMe-Net uses periods of one calendar year and reports a ‘contact prevalence proportion’. This figure represents the proportion of the population that had at least one interference with the GP (e.g., consultation, prescription) for a selected episode (i.e. final diagnosis). This is calculated by dividing the number of persons contacting their GP for a specific health problem during the selected calendar year(s), by the total number of patients in these years. More precisely, the denominator ‘patient years’ combines the number of listed patients in a practice with the length of their registration. This corrects for the dynamic population in a general practice in which patients are born, die, and move in or out of the practice.
Thus, in the methods applied in FaMe-Net, some interference with the GP (practice) is needed in order to be included in the prevalence (‘contact prevalence proportion’) or incidence figures (see below). This method makes these data particularly good for an assessment of the epidemiological representation of illness and conditions under the treatment or surveillance of the GP. For diseases and conditions with a variable course, such as depression, gout, or allergic rhinitis, these methods reflect whether or not the disease is still severe enough to seek medical help. Consequently, medical problems not reported to the GP, e.g. minor problems for which no professional medical help is sought, are not included in these figures. Moreover, a severe disease that is exclusively handled by a specialist (e.g. HIV/AIDS) is also potentially underreported. This effect is probably limited as in most cases the GP receives (yearly) written reports on the situation, or is involved in prescribing medication or monitoring, for example by requesting lab tests.
For assessment of prevalence, the episode label that was recorded at the end of the calendar year is used. For episodes evolving over a longer period of time, and in episodes in which the final diagnosis is harder to make, it should be noted that this might result in some underestimation of the rate of these more severe diagnoses in the first year(s) that this condition is recorded. The Distributions tab page presents prevalence data of episodes.