Original article
Recent epidemiological trends in tuberculous pleural effusion in Galicia, Spain

https://doi.org/10.1016/j.ejim.2012.06.014Get rights and content

Abstract

Objective

Knowledge on the distribution and determinants of tuberculous pleural effusions (TBPE) is incomplete. We aimed to describe the epidemiological trends and individual characteristics of TBPE in Galicia, Spain, over a 10-year period (2000–2009).

Design

A retrospective, observational study based on epidemiological data obtained from the Galician Tuberculosis Register.

Results

There were 1835 cases of TBPE (16.3% of the total 11,241 TB cases reported). The number and incidence of TBPE decreased significantly during the study period, from (262 and 9.6/100,000 inhabitants in 2000, to 133 and 4.8 in 2009, respectively; P < .001 for both). The mean annual decrease in TBPE incidence was 6.9%, and 50% overall. TBPE mainly affected males (63.5%), precisely 61.2% young males between 15 and 44 years. Twenty-five percent had lung involvement (chest X-ray), and 41.7% had a positive sputum culture. A significant increase (P < .001) was observed during the study in the percentage of patients who had more TB risk factors.

Conclusions

The incidence of TBPE decreased significantly during the study period, with no changes in epidemiological characteristics, and with trends similar to the total number of TB cases. The introduction of the Galician Prevention and Control Plan (GPCP) for tuberculosis appears to be effective for better control of TB.

Introduction

Tuberculosis (TB) continues to be one of the most common causes of mortality and morbidity in the World due to infectious cause. In 2009, the World Health Organization (WHO) estimated the burden caused by TB as 9.4 million incident cases, 14 million prevalent cases, and 1.7 million deaths [1]. Socioeconomic factors, the lack of control policies, antibiotic resistance, migrations from high to low incidence countries, and co-infection due to the human immunodeficiency virus (HIV) have contributed to the spreading of TB [2], [3]. The current epidemiological status of TB in Spain is not completely understood. A national total of 8029 cases (18.3/100,000 inhabitants) [4] were notified during the year 2006, but, according to estimates by WHO [5], our country should have an incidence of 30/100,000 inhabitants, which would mean an under-reporting of 39% of cases at the least.

At the end of 1994 the Galician Department of Health began the Galician Prevention and Control Programme (GPCP) for TB [6], aiming to set up a register and active follow-up of all cases, through TB Prevention and Control Units (TBUs). Its aim was to reduce the morbidity and mortality of TB until achieving levels where the disease does not represent a health problem for Galicia, and to match the incidence rate of Western European countries [7]. In 1996, the first year for which data from this programme was available, the incidence of TB was 72.3/100,000 inhabitants [8].

In the 1990s, the most common cause of pleural effusion in our area [9] was tuberculous pleural effusion (TBPE), which is considered as a primary form of TB [10]. Worldwide, there are scarce epidemiological data on the distribution and determinants factors of TBPE. The prevalence of pleural involvement in TB varies between 4% and 87% according to series [11], [12] and it appears to be associated to the differences in the prevalence of TB in the general population [13]. In Galicia, 44% of the TB is extrapulmonary, and the DPTB are the most frequent cause [14]. At an international level, DPTB is considered the second cause of extrapulmonary TB (behind that of TB adenitis) [15], and the reviews on its epidemiology are focused on the influence that HIV infection may have on this form of TB presentation [16], [17], [18].

The aim of the present study is to determine the recent epidemiological trends of TBPE in Galicia, and to analyse the impact of the introduction of the GPCP for TB in our region.

Section snippets

Material and methods

An observational, retrospective cohort study was conducted based on TB epidemiological data obtained from the Galician TB register held in the Control of Transmissible Diseases Department, Department of Innovation and Public Health Management, Galicia Department of Health, by means of two systems: 1) declaration of passive cases, using the official declaration form for reporting to the specific TB surveillance system in Galicia (mandatory declaration), and 2) by an active search of the

Results

The number of TBPE registered throughout the study period was 1835 (16.3% of the total TB cases diagnosed), being the most frequent cause of extrapulmonary TB of the total TB cases (range, 14.3%–19.3%, depending on the year). Their principal characteristics are shown in Table 1. The annual number of cases decreased by 49% in the study period and the trend of this decrease was statistically significant (P = .001). It mainly affected males (63.5%), and in particular those aged between 15 and 44 

Discussion

We report a significant decrease in the incidence of TBPE in Galicia during the last 10 years, a positive outcome occurring without there being any changes in its epidemiological characteristics, with results similar to those obtained with the total TB cases. Therefore, it appears that the introduction of the GPCP has contributed to improve the control of TB.

Learning points

  • TB pleural effusion is the most frequent cause of extrapulmonary TB.

  • The annual number of cases decreased significantly in the study period (ten year period, 2000–2009).

  • Lung involvement in the chest X-ray was seen in 25% of patients, and 41.7% had a positive sputum culture for TB.

  • The most frequent risk factors associated with TBPE incidence annually, were: recent contact with a smear-positive TB individual, alcoholism, and smoking.

  • A significant increase has been observed, over time, in the

Conflict of interest

We submit this work, original from all authors.

We have no any conflict of interest in this work.

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      This is critically important in the context of the known limitations of microbiological tests to prove pleural disease related to Mycobacterium tuberculosis infection. These limitations are well reflected by the results of two Spanish studies which showed that the sensitivity of acid-fast smear and the cultures on solid media for pleural fluid samples were 6% and 36.3%, respectively [8] and 8% and 41%, respectively [9]. Better results were found for nucleic acid amplification tests (NAATs), but the sensitivity of this method is highly variable (37–71%) and still too low to recommend the use of NAATs in routine work-up of patients suspected of TPE [2,10,11].

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