Undetected burden of tuberculosis in a low-prevalence area.

SETTING

Under-ascertainment and under-reporting of tuberculosis (TB) hampers surveillance and control. Case detection is improved by record linkage of case registers and under-reporting can be estimated by capture-recapture (CR) analysis.

OBJECTIVES

To assess the completeness of the TB registration systems and estimation of TB incidence and under-reporting in the Piedmont Region of Italy in 2001.

METHODS

Record linkage of the 'physician notification system', the TB laboratory register and the hospital records register, and subsequent three-sample CR analysis.

RESULTS

Record linkage identified 657 TB cases; CR analysis estimated 47 (95%CI 31-71) unrecorded cases. Under-reporting of the 'physician notification system' was estimated at 21% (95%CI 20-23). The overall estimated TB incidence rate was 16.7 cases per 100000 population (95%CI 16.3-17.3), varying according to the subset investigated: 12.7 for individuals from low TB prevalence countries and 214.1 for immigrants from high TB prevalence countries; 13.1 and 25.8 for persons aged < and > or = 60 years, respectively; and 32.1 in Turin, the regional capital and 10.8 in the rest of the region.

CONCLUSIONS

When multiple recording systems are available, record linkage and CR analysis can be used to assess TB incidence and the completeness of different registers, contributing to a more accurate surveillance of local TB epidemiology.