Enfermedades Infecciosas y Microbiología Clínica
Original articleExtrapulmonary tuberculosis: epidemiology and risk factorsTuberculosis extrapulmonar: epidemiología y factores de riesgo
Introduction
There has been a constant decrease in the number of cases of tuberculosis (TB) in industrialised countries due to improvements in social conditions and the availability of effective antituberculosis drugs.1 This decrease halted between the years 1985 and 1992 due to the relaxation of prevention and control programs, the appearance of HIV infection, and the migratory movements of people from countries with a greater incidence of TB.2, 3 Although the total number of cases of TB has decreased, the reduction in cases of extra-pulmonary tuberculosis (EPTB) has been smaller, resulting in a proportionate increase in EPTB compared to pulmonary tuberculosis (PTB).4 In the cases of TB reported in the US, for example, EPTB accounted for 15.7% of total cases in 1993, but 21% in 2006.5 The reasons for this smaller reduction are little known and have been attributed, among others causes, to demographic changes in the susceptible population and a decreased uptake of vaccination with BCG.6, 7 There are no prospective studies that analyse other possible enhancing factors for EPTB infection.
We present a prospective research study with the following targets:
- 1.
To describe the epidemiology of EPTB in a Caucasian population, comparing the incidence and characteristics of EPTB with those of PTB.
- 2.
To analyse factors contributing to the increased proportion of cases of EPTB.
Section snippets
Method
A specialised unit for following up patients with TB was opened within our hospital in 1991, and a program for prevention and control of TB began in the North West Spanish region of Galicia in 1995. An active search of all the diagnosed cases of TB was performed from 1991 in our health area with a predominantly Caucasian population. In 1991 the population consisted of 218,749 inhabitants, with a mean age of 38.8 years (16.3% older than 64 y); 51.% women (59.9% older than 64 y); 0.29% were born
Results
A total of 2,161 cases of TB were diagnosed. Five (0.23%) cases were in patients born outside Spain. The incidence decreased over time from 79.9 per 100,000 in 1992 (sputum smear-positive 26.3) to 27.1 per 100,000 in 2008 (sputum smear-positive 10). Among the total of 2,161 cases, 705 (32.6%) were EPTB, 1,186 (54.9%) were PTB, 106 (4.9%) were disseminated TB, and 164 (7.6%) were concurrent EPTB-PTB. The number of cases of both EPTB and PTB decreased over time, but EPTB cases decreased more
Discussion
Our data confirms a lower reduction in EPTB compared with the reduction in PTB, in an area with intermediate incidence of TB, a good program for prevention and control of the TB, and predominantly Caucasian population where life expectancy and the proportion of women in the population are increasing. All the diagnosed cases of TB have been reported and the lower reduction in EPTB cases is not due to an increase in the reporting of cases or as a result of over-diagnosis, since the percentage of
Conflict of interests
The authors declare no conflicts of interest related to this study.
Acknowledgments
The first author had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
We would like to thank Ana Del Rio, Consultant Paediatrician, Royal Blackburn Hospital, East Lancashire, United Kingdom, for revision of the translation to English.
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