Objective: development of an algorithm to estimate the prevalence of obstructive lung diseases (OLD) through record linkage of administrative health data sources in three Italian areas.
Setting: AULSS 12 Veneziana, city of Torino, ASL10 Firenze.
Participants: all residents in the three areas in the period 2002-2004 (N = 1,944,471 on 30th June 2003).
Main outcome: crude prevalence, standardized prevalence with 95% confidence intervals.
Methods: the following data sources were used to identify OLD cases: hospital discharges (HD), health-tax exemptions (HTE), death causes (DC) and drug prescriptions (DP). All patients diagnosed with (from HD) or dead because of chronic bronchitis, emphysema and asthma have been included in the analysis. We defined as a prevalent case a subject found in each year in at least one of the four data sources. We reported the absolute and relative contribution of each information system by area, age, gender and year of interest. We performed a sensitivity analysis using more restrictive criteria to identify prevalent cases (two or more DPs per year).
Results: DP was the most relevantsource in identifying cases (from 86 to 88%). The relative contribution ofHD ranged from 3 to 5%. In 2003, standardized prevalence of OLD ranged from 5.35% in Firenze to 6.02% in Venezia. Venezia showed a higher prevalence in children aged 0-14years and a lower prevalence in older age groups (> 64 years) compared to other centers. Overall, the prevalence was higher among males. The use of more restrictive criteria in case identification substantially reduces the estimated prevalence, particularly in younger age-groups and to a lesser extent, in older age-groups.
Conclusions: the algorithm provides estimates with differences between centres. The validity of this algorithm (in terms of sensitivity and positive predictive value) needs to be evaluated through further ad hoc studies.