Incidence of pulmonary tuberculosis: application of the capture-recapture method

To determine as accurately as possible the incidence of pulmonary tuberculosis within Health Area 15 of the Community of Valencia during the period 1990-1993, using the capture-recapture method. Descriptive study on the population of Health Area 15 (population: -139.903) divided into 4 large groups according to age (0-14, 15-34, 34-54 and 55+). Data was obtained from the statutory notification system of infectious disease (SNSID) and from the registry of the said area's Hospital Microbiology SERVICE: The main variable under study was the number of cases of pulmonary tuberculosis, both as notified under the SNSID and in terms of cases in the microbiology register in which M. tuberculosis was isolated. The incidence-rates were calculated by age and year of study for both registries employing the capture-recapture method. The mean annual incidence obtained for the SNSID register during the study period was 15.85 cases x 10(-5), and for the microbiology registry it was 23.29 x 10(-5). When the capture-recapture method was employed the mean annual incidence for the study period was 34.81 x 10(-5) (CI 95%: 31.82-39.92). In each of the years studied the number of cases identified was greater for the microbiology register than for the SNSID. Around half the cases of tuberculosis are below 34 years of age, with the larger section, and that having the highest incidence of tuberculosis being the 15 to 34 years age-group. There is no apparent upward trend in incidence rates calculated for this period. The data from the SNSID system on incidence of pulmonary tuberculosis within Health Area 15 of the Community of Valencia tends to underestimate the true incidence rate. The factual resources of the Hospital Microbiology Service are underutilized, considering the quantity and quality of information it can provide. The capture-recapture method is a good choice of method for measuring tuberculosis incidence. This method merits greater use within the field of epidemiology as much in order to assess the representativeness and thoroughness of surveillance systems as to identify inadequacies in their reporting and localisation of disease outbreaks.