The epidemiology of tuberculosis in Gran Canaria, Canary Islands, 1988-92: Effectiveness of control measures

Abstract

Setting: Since there is no national programme for tuberculosis control in Spain and the epidemiological situation in this country is unknown, a programme against tuberculosis in Gran Canaria (Canary Islands) was started in 1987.

Objective: To analyze the impact of this control programme, particularly the trend of new cases of tuberculosis by age groups and risk factors for 1988-92.

Design: A detailed search of all new cases of tuberculosis was carried out by examining the files of all public and private hospitals and outpatient clinics of the island, the records of the Services of Clinical Microbiology and Pathology of the public hospitals, and the registers of patients with AIDS.

Results: The annual rates of new cases of tuberculosis per 100,000 were 32.2 in 1988 (214 cases), 26.2 in 1990 (174 cases), and 29.4 in 1992 (196 cases), and the rates of sputum-positive cases 13.3 (89 cases), 12 (80 cases) and 15 (100 cases), respectively. The distribution of tuberculosis cases by age peaked in the age groups 40-49 and 30-39 years. Between 1988 and 1992, statistically significant differences were found in the percentage of cured patients (21% [45/214] vs 85.7% [168/196]), patients with a delay in diagnosis > 3 months (40.2% [86/214] vs 21.9% [43/196]), and contacts evaluated (45.3% [97/214] vs 90.3% [177/196]). However, an upward trend in the incidence of tuberculosis for 1990-92 was found in association with an increase of new cases among the homeless, immigrants, and HIV-infected people. When these three population groups were excluded from the analysis, the annual rate for the total population showed a progressive decline from 1988-92.

Conclusions: The data studied here show that successful priority control measures (cure rate, early diagnosis, study of contacts) have been achieved in this island. It is necessary, however, to develop strategies for combating the tuberculosis problem in specific high risk populations.