Epidemiological use of drug prescriptions as markers of disease frequency: an Italian experience.

All Italian citizens are covered by the National Health Service (NHS) and medical records of individual drug prescriptions are routinely collected and processed. A procedure entitled EPIFAR has been developed which, on the basis of a computer routine, makes it possible to trace back the prescription history of each individual included in the NHS. The validity of information gathered through the EPIFAR procedure to provide estimates of tuberculosis (TB) prevalence has been evaluated. A comparison with routine surveillance data has been made. The EPIFAR procedure identified a total figure of TB patients seven times higher than that from official notifications. A sample survey was conducted among the prescribing physicians in order to quantify the proportion of TB cases among subjects receiving prescriptions of anti-TB drugs. According to general practitioner recall 66.4% of the patients were treated because of TB diagnosis, TB prophylaxis and TB relapse.