There was a low contact tracing coverage within the immigrant population during the pre-intervention period. The main reason for that was that the TBPCP was not prepared to manage the large influx of immigrants that ocurred during this period. Moreover, a considerable percentage of the immigrants came from high TB endemic countries and did not speak Spanish. This study shows that immigration is a dynamic phenomenon. In the second period there were fewer patients from North Africa and more young adults. We have also found a statistically significant increase in performed contact tracing among immigrants after the incorporation of CHW. This increase suggests that CHW contributed considerably to the improvement of the prevention activities, due to their communication with cases and their contacts by interpreting and mediating for clinical care and in the community [17
Regarding factors associated with lack of contact tracing, the two specific hospitals which were identified deal with large numbers of immigrants, did not have the appropriate means to perform contact tracing and frequently refered patients to a family doctor for contact tracing. Countries of origin such as India, Pakistan, Maghreb and other non-Latin American countries were also associated to lack of contact tracing performed, possibly because the language skills and the cultural barriers that may influence patient's behaviour in relation to TB. Other factors were homeless and unknown residence. CHW contacted some cases, such as the homeless and those with no known residence, by phone or in person. A lack of contact tracing for all forms of TB was associated with male sex, history of imprisonment, extrapulmonary TB and a normal CXR. Among the few number of patients with incarceration history, the percentage of those without contact tracing reach 78.8%, some of these patients were HIV-infected IDU. The risk factors found in our study are similar to those reported in other studies [19
]. It is important to note that the lack of intervention of CHW is associated with lack of contact tracing in all TB cases and in the sub-group of smear positive cases.
International recommendations from organisations such as the WHO, the Centers for Disease Control and Prevention and the International Union Against Tuberculosis and Lung Disease, suggest the incorporation of health providers, community health promoters, social health workers and outreach health workers in areas with high levels of immigration or with many ethnic groups [21
]. The coordinated action of CHW with PHN and TBPCP doctors has contributed to locating cases and their contacts, as well as to increase treatment adherence. They have improved access to healthcare by ensuring that each patient and their contacts can obtain an individual health insurance card. In our study, the influence of CHW on TB treatment adherence was limited because the percentage of treatment adherence in Barcelona was already satisfactory due directly observed therapy in higher risk patients since 1995 [24
Mass migration has affected the epidemiology of TB. In Spain, a consensus document has been developed to address this problem, even in those with no right of residence. This policy recommends that all migrants have a health card, an initial medical examination at their first appointment and to include CHW in TB control programmes [12
From a multidisciplinary perspective, the incorporation of CHW can reinforce the effectiveness of PHN personnel and minimise difficulties accessing care [26
]. Similarly, the "IEC" approach (information, education, communication) develops both care and community level actions, such as health promotion in TB [27
]. The educational sessions in private homes and associations for immigrants have reached the target population in their daily settings outside of working hours [29
]. Mediation, conflict resolution, linguistic translation and cultural interpretation has improved the relationship between patients and health care personnel and has reduced communication related issues.
The CHW strategy ensures that patients who were from a different culture are supported, accompanied and defended confronted with TB stigma and social and occupational discrimination. The strategy offers community-based educational support in which patients are actors controlling TB transmission and confirms that TB is, above all, a social process involving multiple context-related factors of healing and control over transmission [30
One study limitation was the variation in characteristics between both periods; an increase of cases between 25-39 years of age, from Latin America and India, Pakistan and from inner-city in the CHW group. The increase in immigrants would most likely have worsened contact tracing and therefore our figures may have underestimated the benefit of the CHW intervention. Eight percent of cases were not contacted, despite multiple phone calls and home visits. However, given the high mobility of immigrant groups, this is considered a low percentage.
The effectiveness of TB programs depends upon their ability to adapt to the emerging needs of the population changes. Therefore, it is recommended incorporate CHW into every TB program with the goal of improving TB control in immigrant populations. This can also be extended to other infectious diseases such as HIV, sexually transmitted diseases and malaria. CHW incorporation can also save social and economic costs in TB programs, however studies on cost-effectiveness of the CHW interventions in the TB programs are also necessary [32