[The quantification of tuberculous disease in an Italian area and the estimation of underreporting by means of record linkage].

The description and interpretation of tuberculosis spatial and temporal variations in Italy is rather difficult because of well-grounded suspicions of disease underestimation, related with the bad working of the compulsory notification system. In this study, the record-linkage technique was used to estimate the proportion of TB undernotification in an Italian area, in order to give a first quantitative estimate of tuberculosis at a geographical level. The area considered was the Local Health Agency of Florence (population in 1994: 803,588) in 1995. Information for record-linkage was taken from: the Regional TB Archive, Hospital Discharge files, Laboratories, Pathology Departments, the Regional AIDS Registry, the Regional Mortality Registry. The linkage among the different sources was based on first and last name, date and place of birth, or only on first and last name for the laboratories. Prevalent cases and relapses were excluded through comparison with various historical archives. Most cases signalled only in hospital discharges were re-evaluated through original medical records. In such a way, the original sample was reduced from 690 to 182 cases incident in 1995, diagnosed in the area considered, and mostly resident in the same area. Among these cases, 98 (53.8%) were unknown to the compulsory notification system. The most of them come from hospital departments (27 cases) and from laboratories (47 cases). Fourty-nine of the unknown cases concerned pulmonary TB. The notification rate in the area moves then from 10.5/1000 to 22.7/1000.